The Last Common Ancestor of Chimps and Humans?

Co-Authored with the New Bing

A question that is often asked of anthropologists is how related we are to chimpanzees, bonobos, and the other great apes. The answer is that we are very related, in fact, we share 98% of our DNA with chimps and bonobos. But why is this? The short answer is that we share a recent last common ancestor, or “LCA”, this means that our two species diverged from the same ancestor somewhat recently in geologic time, about 6-7 million years ago.

The last common ancestor of chimps and Homo sapiens is a fascinating topic in Paleoanthropology, as it sheds light on our closest living relatives’ evolutionary history and divergence. However, identifying and characterizing this ancestor is difficult, as many uncertainties and controversies surrounding its morphology, behavior, ecology, and genetics exist.

One of the first challenges is to estimate when the last common ancestor (LCA) lived. This can be done by comparing the DNA sequences of living, also known as extant, humans and chimps and calculating how long it would take for them to accumulate the observed differences due to mutations. This method, known as the Molecular Clock, gives the LCA an approximate date of 6 to 7 million years ago (mya). However, this date may not be accurate, as different genes may evolve at different rates, and there may have been episodes of gene flow or hybridization between the two lineages after their initial split. Therefore, fossil evidence is also crucial to corroborate or refine the molecular estimates.

Unfortunately, the fossil record of the LCA and its early descendants is very scarce and fragmentary. Most of the fossils that have been attributed to this period are from Africa, where the LCA is presumed to have originated. However, some recent discoveries suggest that Europe may also have played a role in the evolution of hominins (the human clade). For example, Graecopithecus, a fossil ape from Greece and Bulgaria, has been dated to about 7.2 mya and has some dental features that resemble those of hominins. Some researchers have proposed that Graecopithecus may represent the LCA or a close relative, implying that the split between humans and chimps occurred in Europe rather than Africa. However, this hypothesis is controversial and not widely accepted by most Paleoanthropologists.

Another challenge is to reconstruct what the LCA looked like and how it behaved. Many researchers have assumed that the LCA was similar to a modern chimpanzee, based on the idea that chimps have retained more primitive traits than humans. However, this view has been challenged by recent studies that show that both humans and chimps have evolved many unique features since their divergence from the LCA. For example, chimps have more genes modified by natural selection than humans, suggesting that they have adapted to their specific environments and lifestyles. Moreover, chimps exhibit a great diversity of behaviors across different populations and regions, indicating that they are not static or uniform in their culture and ecology.

Therefore, it is likely that the LCA was different from both humans and chimps in many aspects. Some possible characteristics of the LCA that various researchers have suggested are:

– It was bipedal, at least partially, as this trait is shared by all hominins and may have originated before the split from chimps.

– It had a relatively small brain size, similar to or slightly larger than that of a modern chimp.

– It had a mixed diet of fruits, leaves, nuts, seeds and animal foods, as indicated by its dental morphology and isotopic signatures.

– It lived in a mosaic habitat of woodlands and grasslands, as inferred from its locomotion and diet adaptations.

– It had a complex social structure and communication system, as these are common features of all apes and may have been present in their common ancestor.

Of course, these are only tentative hypotheses based on limited evidence and may change as new fossils and genetic data are discovered. The LCA remains a mysterious and elusive entity in our evolutionary history, but also a fascinating one that can help us understand ourselves better.


– The last common ancestor of humans and chimps probably wasn’t much like either – Science News

– Gorilla–human last common ancestor – Wikipedia

– Here’s What the Last Common Ancestor of Apes and Humans Looked Like – Live Science

The Story of Us-Survival Archaeology with Dr. John Shea

On this episode #TheStoryofUs , we are joined by well-known Paleoanthropologist Professor John Shea, a prominent lithic and survival expert. We talk about his new book, The Unstoppable Human Species. It details our evolution and survival through the lens of function over what was required to survive in the harsh environments that our forebears found themselves in. We learn about stone tool industries, what they are, and what they are not. We travel through time and see what it would have been like to be in some of the situations that our ancestors were in, and to see how we would deal with it today – to realize it is not all that different! We had a great chat; I loved having Dr. Shea on, and his book was a joy to read, and I can’t wait for you guys to watch this chat and learn something new! I know I sure did! Remember, there is always more to learn!

To grab a copy of Dr. Shea’s new book, you can find it here:

See you guys next time! Be sure to like and subscribe for more episodes, and hit that reminders button never to miss a new episode!

Thoughts on Human Hibernation

Hibernation is a word many of us will be familiar with, as it is a strategy that some animals living today in Northern latitudes employ to cope with the harsh winter months. However, does there exist potential for humans to hibernate too? And beyond that, did any of our ancient hominin relatives do so in order to deal with the climate? A paper from 2020 in the journal L’Anthropologie comes to the surprising conclusion that ancient humans were hibernating 1(Bartsiokas & Arsuaga, 2020). Whilst there had been studies that introduced the potential for human hibernation within a laboratory setting, and under certain conditions for a short period of time, it is the first comprehensive investigation into whether hibernation actually occurred in ancient humans1.

The authors of the study, recognised that many hibernators will suffer from chronic kidney disease as a result of excessive fattening and starvation associated with hibernation, and sought to test this by analyzing the bones of humans from Sima de los Huesos1. They looked at a number of significant skeletal pathologies (injuries or diseases that affect the skeleton and are evident from the bones) that are supposed to be indicative of chronic kidney disease and hibernation as a whole1. Some of these, the authors of the paper described as diagnostic1. However, even the pathologies deemed to be diagnostic may not be such good indicators of hibernation.  Firstly, one of the pathologies the authors of the hibernation hypothesis used as an indicator of hibernation was “Lines of Arrested Growth” (lines which indicate areas of little or no growth in the bones that supposedly represent starvation)  which may have causes other than starvation 1, 2(Papageorgopoulou et al., 2011) . Rather in humans it seems to be caused by normal growth patterns and hormonal change 2. Two papers, one from the American Journal of Human Biology and one from the American Journal of Physical Anthropology (now the American Journal of Biological Anthropology) from 2011, discuss the reliability of Lines of Arrested Growth for studying times of stress in populations  2, 3( Alfonso-Durruty, 2011). The authors of the first paper analyzed 241 tibiae from medieval skeletons in Switzerland, only selecting tibiae free from all other skeletal pathologies for X-ray images 2. They compared the number of Lines of Arrested Growth and frequency of Linear Enamel Hypoplasia (a condition that arises from malnutrition and certain diseases which causes the enamel to not properly develop forming horizontal lines on the teeth) per skeleton 2. In addition, the authors of that paper also looked at the skeletons to discern whether the bones had pathologies that represented an underactive thyroid condition 2. They found no correlation between Linear Enamel Hypoplasia and Lines of Arrested Growth which is to be expected if Lines of Arrested Growth are not caused by starvation 2. Whilst they also found that there was a raised level of underactive thyroid condition amongst the skeletons, the number of Lines of Arrested Growth did not reflect the significantly lower life expectancy that is to be expected if it were to represent a skeletal symptom of underactive thyroid condition in a society without the modern understanding of medical care 2. Overall the authors of that paper found no correlation between other symptoms of disease or starvation, growth inhibiting diseases or starvation and Lines of Arrested Growth 2. The authors of the second paper chose three groups of New Zealand White rabbits, with each group being kept under different conditions 3. The first was a control test where the rabbits were kept in standard laboratory conditions whilst the second was fed a low quality diet and the third were periodically starved 3. New Zealand White rabbits develop in a similar pattern to humans and are very responsive to starvation, meaning they are more likely to develop clearer Lines of Arrested Growth 3. The authors found that overall growth in the skeleton of the rabbits was not hampered by the poor diet and that there was no significant difference in Lines of Arrested Growth between the groups 3. Both of these studies demonstrate that Lines of Arrested Growth do not give an accurate view as to an individual’s health and whether or not they have previously been through a period of starvation or disease. This stands true of bones of deceased individuals far in the past. 

‘Osteocytic osteolysis’ (a type of bone resorption) is another characteristic pathology that the authors of the hibernation hypothesis described as diagnostic of hibernation1.  However, despite the fact that it can indicate remaining stationary for a long period of time, it has other causes such as lactation by mothers, hyperparathyroidism, Vitamin D deficiency and Calcium deficiency 4(Tsourdi et al., 2018). These factors cannot be ruled out and have causes other than hibernation, as they occur in modern day people.    

A simple but alternative hypothesis for skeletal pathologies associated with Chronic Kidney Disease or any other aspect of hibernation, is that the humans went through seasonal starvation and fattening whilst remaining active, albeit less so. An animal, or in this case humans, could employ this strategy to deal with the winter months. This can be seen in the Svalbard reindeer, whose Spring body mass is lower than their Autumn body mass by as much as 25 kg. Additionally, Muskox lose 40% of their body weight in Winter and then subsequently gain it back in Summer and Autumn in preparation for the next freeze 5,6(Norsk PolarInstitutt, n.d.: Adamczewski, 1992). These periods of fattening and starvation could theoretically still elicit the same response from the bones if the changes in body mass were drastic enough. A way to test this would be to study the bones of species that utilize this method and compare them to similar species that hibernate, or contrast individuals of different sexes within the same species where one hibernates and the other does not. For example, the skeletal pathologies of female polar bears could be compared to those of male polar bears, as male polar bears do not hibernate whilst female polar bears do7(Robbins, 2012) However the authors of the hibernation hypothesis had an answer for such a proposal1. They state that “starvation, (without lack of sunlight),  often leads to vitamin deficiencies such as beriberi, pellagra and scurvy but cannot lead to Vitamin D deficiency”1. The expectations that Vitamin D deficiency is not present where there are adequate light levels and that starvation cannot contribute to Vitamin D deficiency do not align with two fairly recent papers 8,9(Pereira-Santos, et al  2019: Kueper, et al, 2015). The authors of the first paper found that the percentage of the population affected by “vitamin D deficiency and insufficiency in this country was similar to that of nations with reduced solar availability”, suggesting diet and nutrition played a role in vitamin D deficiency8. The other paper found that vitamin D levels were depleted in more extreme cases of anorexia, and that supplementation could help alleviate products of anorexia, such as osteopenia and osteoporosis, indicating a strong dietary component of vitamin D deficiency9.  What this all indicates is that even where light levels seem adequate, they may not have been, and diet is and likely has been a significant part of sourcing vitamin D, leaving potential for the hominins to have undergone famine whilst remaining active. This is especially the case in a climate that was colder than today where light levels would likely be lower and famine would have been more common 10,11(Hosfield, 2020: Candy, Schreve, & White, 2015).

The idea of deep snow drifts and billowing blizzards should not be pictured when thinking of a classic winter endured by the hominins at Sima de los Huesos, as the winters during that period of time were typically dry10. While colder on average than the region today, most winters at Atapuerca would not be all that different from Winters at present in the area10. Life under such conditions would be hard without modern comforts but by no means an agonizing slog that could only be endured through hibernating. However, if we are to accept the older dates of the occupation of the site by Homo heidelbergensis and line them up with the younger dates of occupation in a chronological sequence, and then assume consistent occupation for most of the time, then there is the implication that these humans lived through roughly 20,000 years of an extreme cold period known as Marine Isotope Stage (MIS) 13 to MIS 12 10,11,12,13,(Berger et al., 2008: Arsuaga et al., 2014).  Temperature estimates for sites in winter a little way North in the UK sit between −10 and −36°C11. It is unclear how this would have affected the temperature at Atapuerca and Northern Spain as a whole, but it is likely that there would be months where the temperature was sub zero10,11. It is worth mentioning that what we know about the climate of the area from the time is largely available to us from other sites and a number of Atlantic core samples11

When considering the skeletal pathologies of Homo heidelbergensis it is important to recall that the scarcity of resources during the winter months would limit access to a varied diet containing plant foods. It is possible that H. heidelbergensis was largely dependent on red meat as a food source in the coldest seasons. Undoubtedly there was red meat available, with Aurochs (giant wild ox), at least one species of bison, a species of giant deer, the list goes on14-18(Domingo et al., 2017: Rodríguez-Gómez et al., 2017: García & Arsuaga, 2011: Rodríguez et al., 2011: Van der Made, 2013). This is significant because diabetes, one of the leading causes of chronic kidney disease today, can be caused by an overconsumption of red meat 19,20,21,22(Webster, et al., 2017: Kovesdy, 2022: Evans & Taal, 2011: Feskens, Sluik, & van Woudenbergh, 2013). Diabetes makes up between 30-50% of all cases of chronic kidney disease19. It is estimated that for every 100g of red meat that is consumed daily, the percentage of risk of developing diabetes goes up by 13%22. If we are to take the upper amount of calories that the humans at Sima de los Huesos would have to consume it would sit in the region of between 3000 kilocalories (kcal) and 5500 kcal based off of estimates for their descendents (the Neanderthals) 23(Sorensen & Leonard, 2001). From there we can work with a mid range estimate of about 4250 kcal. There are approximately 1450 kcal in a kilogram of Bison meat although it should be worth mentioning that this is an average extrapolated from a whole bison and it undoubtedly could be higher or lower based on the specific part of the body 24(Henrikson, 2004). It is also worth mentioning that the hominins would likely be eating other animals as well and that Bison meat is only used to estimate the risk of developing chronic kidney disease. However once we accept this is only an estimate we can divide the mid range estimate for daily calorie requirements by the kilocalories per kilogram of Bison meat then we get the kilograms of Bison meat required each day which is 2.93kg. Then we convert it to grams and divide it by the 100g mentioned earlier. This gives us 29.3 which we then multiply by the 13% of risk of developing diabetes per 100g of red meat consumed daily23. It should be discussed that the risk of developing diabetes may be different for the Sima de los Huesos hominins than for modern humans so this does rely on the assumption that it is the same. This gives us 381% which is the percentage at which we can expect diabetes to be higher in the Sima de los Huesos population. 381% is then multiplied by 0.4 as the percentage of diabetes cases that develop into chronic kidney disease is 40%19,20. The result is 152% which is the percentage at which  chronic kidney disease can be expected to reach if such humans were eating a largely meat based diet. Now we convert this to a decimal and multiply it by the percentage of the population today that have chronic kidney disease. This is 11% so 11 multiplied by 1.52 is 16.72%17. So therefore we can expect chronic kidney disease cases to represent about 1:5 of the hominins at Atapuerca, which is a significant proportion, and when taken together with evidence against the techniques used by the authors of the hibernation hypothesis, this certainly makes for an interesting alternative proposal. However, eating that much red meat would have other consequences such as protein poisoning and overdose of Vitamin A which would undoubtedly affect the bones causing osteoporosis 25(Hockett, 2012). This suggests it could only be maintained if the humans subsisting off of this diet did so for short periods of time. There is also the potential that the 40% figure for diabetes resulting in chronic kidney disease is an overestimation as a paper suggested that at least some of the cases of chronic kidney disease in diabetics may not have a causal relationship20. In addition, the extreme cold period MIS 13 to 12 only lasted for 20,000 years from 470,000 years ago and does not encompass all of the human activity at Sima de los Huesos, so there would not necessarily be the need for the hominins to consume excessive amounts of meat all of the time11.  

The authors of the hibernation hypothesis also use the representation of adolescent skeletons at Sima de los Huesos1.  On fairly recent archaeological sites where adolescents are significantly underrepresented in the site’s archaeological record, there is an important  connection between preservation and assignment of age to the skeletons 26(Lewis, 2016). To quote Mary Lewis from her 2016 paper26

“Late fusing epiphyses (i.e. the end of the clavicle nearest the sternum, or first vertebra of the sacrum) used to identify an individual as a ‘young adult’ are less likely to survive than the features of mature age, such as osteoarthritis, meaning that it is likely many more young adults are consigned to the ‘adult’ age category than any other age group.”

It is to be inferred that such diagnostic features of adolescence would be not only easier to spot, but also present to a much greater degree on sites with far better preservation. From that it can then further be inferred that a more substantial percentage of skeletons would be adolescent in an environment with better preservation such as Sima de los Huesos. However this on its own may not be enough to account for the high adolescent death rate as the adolescent mortality consists of roughly 1:2 of the hominin assemblage when looking at the craniums alone1,13. Perhaps a better suggestion is that there is high adolescent mortality in societies without modern medicine, particularly in cases of low genetic diversity. A famous case of this would be of Charles Darwin’s family where, despite being a wealthy family, three of his children died during childhood including one dying during adolescence 27(Bogin, 2012). This is even more present when one looks at the percentage of mortality that children under 15 made up 28(Roser, 2019). This figure was almost 50% just a century ago and includes juveniles and early adolescents28. In addition, one archaeological site known as “Indian Knoll” in Kentucky, USA, suggests that the death rate before adulthood was even higher in some prehistoric hunter gatherer populations28. The highest proportion of mortality for any society before or at the beginning of the 20th century was by far that of infant mortality with 27% newborns dying in their first year of life28. So hypothetically we should expect to see high numbers of fossil remains of newborns and young children amongst the Sima de los Huesos collection if it represented the demographics that died in the cave. However newborns often do not fossilize well, which could equate to a misleading death assemblage demographic 29(Halcrow et al. 2020). This is backed up by the underrepresentation of newborns and infants in the fossil record where at the most 300 of the 6000 hominin individuals found so far are newborns or infants 29,30(Smithsonian Institution, 2022). This is equivalent to 5% nearly a sixth of what the true representation should be.

Another point worth mentioning is anatomically modern hunter gatherer societies and tribes often collaborate to take care of the ‘juveniles’ and adolescents, and with anatomically modern humans’ extended ‘juvenile stage’, while these members of the group are semi-independent, they are still unable to meet their daily caloric intake and so members of a group are required to aid them in obtaining enough food27. However this may not have been the case for highly mobile lower paleolithic hunter gatherers like the Sima de los Huesos hominins. The argument can be made that the adolescent proportion of the population of hominins at Sima de los Huesos may have represented a larger percentage of the overall living population and so played a more significant role in obtaining the group’s daily calorie requirements, resulting in them disproportionally often facing down the prey they were hunting, in addition to coming into conflict with other groups of humans and rival predators. This competition between rivaling groups of humans and other predators may have also resulted in a deficiency in the hunting ecology of Atapuerca as a whole. This could likely cause many of the humans found in Sima de los Huesos to be unable to meet their daily caloric demands, explaining both the pathologies on the hominins and the distribution of mortality being biased towards adolescent hominins. There is some evidence of this from the overall stability of the surrounding ecosystem, where total caloric demands for the predators would have been greater than that of the caloric availability15. What this means is that it would have been a daily struggle for the hominins of Sima de los Huesos, contending with either starvation or being forced to compete with voracious predators, some of which could have easily eaten them15.

Another possibility is that the opposite is true and many of the adolescents and juveniles at Sima de los Huesos died when the group encamped at the entrance of the cave, and adult hominins are rather the anomaly in the sense that there is less of them because many of them would be hunting and so likely dying away from the cave. A worthwhile approach would be to compare Sima de los Huesos to other hominin bearing cave sites similar to it, both at Atapuerca and in other parts of Spain and Europe from the same time period, in order to better rule out a bias in the fossil record from a circumstance such as type of camp placement and age related duties. This is a particularly important argument as, when we look at Neanderthal remains from later on sites, it appears that on the whole there is a bias in the fossil record towards adolescent individuals31(Trinkaus, 1995). However there are only a few sites where adolescent mortality is abnormally high, and at these sites it is so raised that it skews the overall data for Europe31. When sites are weighted against each other this abnormal adolescent mortality rate drops significantly across Neanderthal sites31. Despite this, young adult mortality remains high even after the sites are weighted31. Such a high proportion of mortality in the young adult population that is not mitigated by the weighting of sites suggests a more accurate representation of death rates and life expectancy31. What this all means is that a greater understanding of overwintering behaviors, such as hibernation, could be better grasped by using a larger sample size and properly weighting sites (particularly those that are population dense), and that one site with abnormal adolescent death rate is not enough to extrapolate from. 

So the question now stands: how did the Sima de los Huesos hominins end up in the cave?

The remarkably low amount of carnivore activity that is present on the bones suggests that they were not transported to the cave by a predator or scavenger 32(Sala et al, 2023). If anything the fossils appear to have been scavenged within the cave, likely by bears when the bodies had largely decayed32. The presence and high representation of hand and foot bones indicates the bodies of the hominins were transported to the cave intact as these are elements that are among the first to disarticulate32. The fact that the preservation of the hand and foot bones is better than that of other ancient sites, even those involving burial of hominin remains suggests the bodies were buried in the cave and were only accessed later by the bears32.  

In conclusion, did the Sima de los Huesos hominins hibernate all those many millennia ago? Honestly, it is hard to tell, but as the case I have made here clearly shows, there is currently not enough evidence to point to hibernation as being an overwintering behavior that these hominins practiced. Often in these cases it is the simplest scenario that has the most credibility so here I apply Ockham’s razor :  the case for seasonal starvation whilst remaining active is yet to be rebutted, therefore this is the explanation I have to go with.  


  1. Bartsiokas, A., & Arsuaga, J. L. (2020). Hibernation in hominins from Atapuerca, Spain half a million years ago. L’Anthropologie, 124(5), 102797.
  2. Papageorgopoulou, C., Suter, S. K., Rühli, F. J., & Siegmund, F. (2011). Harris lines revisited: Prevalence, comorbidities, and possible etiologies. American Journal of Human Biology, 23(3), 381–391.
  3. Alfonso-Durruty, M. P. (2011). Experimental assessment of nutrition and bone growth’s velocity effects on Harris lines formation. American Journal of Physical Anthropology, 145(2), 169–180. 
  4. Tsourdi E, Jähn K, Rauner M, Busse B, Bonewald LF.  (2018). Physiological and pathological osteocytic osteolysis. J Musculoskelet Neuronal Interact. 18(3):292-303.
  5. Norsk PolarInstitutt. “Svalbard reindeer (Rangifer tarandus platyrhynchus)”. March 07 2023, n.d. Svalbard reindeer – Norsk Polarinstitutt ( 
  6. Adamczewski, J., A. Gunn, B. Laarveld, and P. F. Flood. “Seasonal changes in weight, condition and nutrition of free-ranging and captive muskox females.” Rangifer 12, no. 3 (1992): 179-183.
  7. Robbins, Charles T., Claudia Lopez-Alfaro, Karyn D. Rode, Øivind Tøien, and O. Lynne Nelson. “Hibernation and seasonal fasting in bears: the energetic costs and consequences for polar bears.” Journal of Mammalogy 93, no. 6 (2012): 1493-1503. 
  8. Pereira-Santos, Marcos, José Yure Gomes dos Santos, Gisele Queiroz Carvalho, Djanilson Barbosa dos Santos, and Ana Marlúcia Oliveira. “Epidemiology of vitamin D insufficiency and deficiency in a population in a sunny country: Geospatial meta-analysis in Brazil.” Critical reviews in food science and nutrition 59, no. 13 (2019): 2102-2109. doi:
  9. Kueper, Janina, Shaul Beyth, Meir Liebergall, Leon Kaplan, and Josh E. Schroeder. “Evidence for the adverse effect of starvation on bone quality: a review of the literature.” International journal of endocrinology, 2015, Article ID 628740 (2015). 
  10. Hosfield, R. (2020). The earliest Europeans – a year in the life: seasonal survival strategies in the Lower Palaeolithic. Oxbow Books, Oxford, pp416. ISBN 9781785707612 Available at: 
  11. Candy, I., Schreve, D., & White, T. S. (2015). MIS 13–12 in Britain and the North Atlantic: understanding the palaeoclimatic context of the earliest Acheulean. Journal of Quaternary Science, 30(7), 593-609.
  12. Berger, G. W., Pérez-González, A., Carbonell, E., Arsuaga, J. L., de Castro, J. M. B., & Ku, T. L. (2008). Luminescence chronology of cave sediments at the Atapuerca paleoanthropological site, Spain. Journal of Human Evolution, 55(2), 300-311. Doi:     
  13. Arsuaga, J. L., Martínez, I., Arnold, L. J., Aranburu, A., Gracia-Téllez, A., Sharp, W. D., … Carbonell, E. (2014). Neandertal roots: Cranial and chronological evidence from Sima de los Huesos. Science, 344(6190), 1358–1363. 
  14. Domingo, L., Rodríguez-Gómez, G., Libano, I., & Gómez-Olivencia, A. (2017). New insights into the Middle Pleistocene paleoecology and paleoenvironment of the Northern Iberian Peninsula (Punta Lucero Quarry site, Biscay): A combined approach using mammalian stable isotope analysis and trophic resource availability modeling. Quaternary Science Reviews, 169, 243–262. 
  15. Rodríguez-Gómez, G., Rodríguez, J., Martín-González, J. A., & Mateos, A. (2017). Carnivores and humans during the Early and Middle Pleistocene at Sierra de Atapuerca. Quaternary International, 433, 402–414.
  16. García, N., & Arsuaga, J. L. (2011). The Sima de los Huesos (Burgos, northern Spain): palaeoenvironment and habitats of Homo heidelbergensis during the Middle Pleistocene. Quaternary Science Reviews, 30(11-12), 1413–1419.  
  17. Rodríguez, J., Burjachs, F., Cuenca-Bescós, G., García, N., der Made, J. V., González, A. P., Blain, H.-A. ,  Expósito, I., López-García, J.M.,  Antón, M.G.,  Allué, E., Cáceres, I.,  Huguet, R.,  Mosquera, M., Ollé, A.,  Rosell,J.,  Parés, J.M.,  Rodríguez, X.P.,  Díez, C.,  Rofes, J.,  Sala, R., Saladié, P.,  Vallverdú, J.,  Bennasar, M.L.,  Blasco, R.,  Bermúdez de Castro J.M., Carbonell, E. (2011). One million years of cultural evolution in a stable environment at Atapuerca (Burgos, Spain). Quaternary Science Reviews, 30(11-12), 1396–1412.
  18. Van der Made, J. (2013). First description of the large mammals from the locality of Penal, and updated faunal lists for the Atapuerca ungulates–Equus altidens, Bison and human dispersal into Western Europe. Quaternary International, 295, 36-47.
  19. Webster, A. C., Nagler, E. V., Morton, R. L., & Masson, P. (2017). Chronic kidney disease. The lancet, 389(10075), 1238-1252.   
  20. Kovesdy, C. P. (2022). Epidemiology of chronic kidney disease: an update 2022. Kidney International Supplements, 12(1), 7-11. 
  21. Evans, P. D., & Taal, M. W. (2011). Epidemiology and causes of chronic kidney disease. Medicine, 39(7), 402-406. 
  22. Feskens, E. J., Sluik, D., & van Woudenbergh, G. J. (2013). Meat consumption, diabetes, and its complications. Current diabetes reports, 13, 298-306.
  23. Sorensen, Mark V., and William R. Leonard. “Neandertal energetics and foraging efficiency.” Journal of human evolution 40, no. 6 (2001): 483-495. 
  24. Henrikson, L. Suzann. “Frozen bison and fur trapper’s journals: building a prey choice model for Idaho’s Snake River Plain.” Journal of Archaeological Science 31, no. 7 (2004): 903-916. 
  25. Hockett, Bryan. “The consequences of Middle Paleolithic diets on pregnant Neanderthal women.” Quaternary International 264 (2012): 78-82. 
  26. Mary Lewis (2016) Work and the Adolescent in Medieval England ad 900–1550: The Osteological Evidence, Medieval Archaeology, 60:1, 138-171, DOI: 10.1080/00766097.2016.1147787
  27. Bogin, Barry 2012. “Childhood, Adolescence, and Longevity: A Chapter on Human Evolutionary Life History”, Adolescent Identity. Edited by Hewlett, Bonnie L. pp. 1-15. New York: Routledge. 
  28. Roser, Max, “Mortality in the past – around half died as children”, Our World in Data, June, 11, 2019 Mortality in the past – around half died as children – Our World in Data 
  29. Smithsonian Institution “Human Fossils”, June, 30, 2022, Human Fossils | The Smithsonian Institution’s Human Origins Program
  30. Halcrow, Siân, Ruth Warren, Geoff Kushnick, and April Nowell. “Care of infants in the past: Bridging evolutionary anthropological and bioarchaeological approaches.” Evolutionary Human Sciences 2 (2020): e47.
  31. Trinkaus, Erik. “Neanderthal mortality patterns.” Journal of Archaeological science 22, no. 1 (1995): 121-142. Doi:   
  32. Sala, Nohemi, Ignacio Martínez, Carlos Lorenzo, Rebeca García, José Miguel Carretero, Laura Rodríguez, Asier Gómez‐Olivencia et al. “Taphonomic skeletal disturbances in the Sima de los Huesos postcranial remains.” The Anatomical Record (2023). 

Ghost DNA and Human Evolution

Coauthored with the New Bing

What is a ghost lineage in terms of human evolution? How is ancient DNA obtained, and how do we know who is missing? What evidence do we have to support whom we think the species is? Has the species been identified? How long ago did this introgression of DNA occur? What does it mean for our genetics today?

A ghost lineage is a hypothesized ancestor in a species lineage that has yet to leave any fossil evidence yet can be inferred to exist because of gaps in the fossil record or genomic evidence. [1] The process of determining a ghost lineage relies on fossilized evidence before and after the hypothetical existence of the lineage and extrapolating relationships between organisms based on phylogenetic analysis. [2] Ghost lineages assume unseen diversity in the fossil record and serve as predictions for what the fossil record could eventually yield; these hypotheses can be tested by unearthing new fossils or running phylogenetic analyses. [3]

Ancient DNA is obtained from fossils or other preserved remains of extinct organisms, such as bones, teeth, hair, skin, or shells. [4] Ancient DNA can reveal information about the genetic relationships, evolutionary history, and demographic patterns of extinct lineages. [4] However, ancient DNA is often degraded, contaminated, or scarce, making it challenging to analyze and interpret. [4]

We do not know who is missing from the fossil record because fossils are rare and incomplete. Fossils only form under certain conditions, such as rapid burial and mineralization, and they are often destroyed by erosion, weathering, or human activity. [5] Therefore, the fossil record is biased towards certain organisms, environments, and periods and does not reflect the true diversity and complexity of life on Earth. [5]

One way to infer the existence of ghost lineages is to compare the genomes of modern humans with those of extinct human relatives, such as Neanderthals and Denisovans. [6] By identifying segments of DNA that are shared or different among these groups, we can estimate when they diverged from each other and when they interbred. [6] For example, researchers found a “ghost population” that interbred with the ancestors of modern West Africans by detecting statistical anomalies in their genomes that were best explained by hybridization with an unknown ancient human lineage. [6]

The ghost population that interbred with West Africans has yet to be identified, as no fossils or ancient DNA samples have been found that belong to this lineage. [6] However, based on genomic analysis, the researchers estimated this ghost lineage diverged from the ancestors of Neanderthals and modern humans up to 1.02 million years ago and interbred with the ancestors of modern West Africans from 124,000 years ago up to the present day. [6]

The introgression of DNA from ghost lineages into modern humans may have had various effects on our genetics today. For example, some genes from Neanderthals and Denisovans may have conferred adaptive advantages to modern humans in certain environments or against certain pathogens. [7] On the other hand, some genes from extinct lineages may have been incompatible with modern human genes or reduced fertility in hybrids. [7] Moreover, some ghost lineage genes may not significantly affect current human traits or functions. [7]

So what does this all mean? It is not just possible, but more than likely, that other hominins have yet to be discovered, which have played an essential role in our evolution. We can learn more about this possible enigmatic species when we get aDNA. Being able to find DNA, which we can now even gather from sediments, we can learn a great deal about where we came from. But once we have that DNA, we can determine who these ghost lineages are, and with that information, the mystery will continue.

There are many gaps in the fossil record; the only way to fill those gaps is by going into the field and exploring and discovering what there is to learn. DNA can reveal so many mysteries about our ancestors and help show what is in store for us in the future.


[1] Ghost lineage – Wikipedia

[2] University of California Museum of Paleontology – Ghost lineages

[3] Nature – Ghosts in the machine

[4] Nature Education – Ancient DNA: The first three decades

[5] Understanding Evolution – The nature of the fossil record

[6] Inside Science – Genetic Traces of Mysterious Human Lineage Detected in People Living in West Africa

[7] Nature – The genomic landscape of Neanderthal ancestry in present-day humans

The First Homo?

Coauthored with the New Bing.

Who was the first “Homo”? Was it Kenyanthropus platyops? Was it the maker of the Lomekwian tools? Is it the ancestor of the 1470 fossil? They seem to share many features, so is it possible that this fossil belongs to that species? What others species are potential contenders? Why? Why not?

These are some of the intriguing questions that paleoanthropologists are trying to answer by studying the fossil and archaeological evidence of our early ancestors and relatives. The origin of the genus Homo is one of the most debated topics in human evolution, as different lines of evidence may suggest different scenarios. In this blog post, I will review some of the main hypotheses and arguments based on current knowledge.

The Kenyanthropus platyops, a 3.5 to 3.2-million-year-old (Pliocene) hominin fossil discovered in Lake Turkana, Kenya. (Photo by: Universal History Archive/Universal Images Group via Getty Images)

The first “Homo” is usually defined as a hominin (a member of the human lineage after it split from the chimpanzee lineage) that has a larger brain size, a more rounded skull, a flatter face, smaller teeth and jaws, and a more advanced stone tool technology than earlier hominins. However, these features did not appear all at once or in a single species, but rather evolved gradually and variably in different populations over time. Therefore, identifying the first “Homo” is not straightforward, as different criteria may lead to different conclusions.

One of the oldest fossils that has been assigned to the genus Homo is a lower jawbone (LD 350-1) found in Ethiopia and dated to about 2.8 million years ago. This specimen has some features that are similar to later Homo species, such as smaller molars and a more symmetrical shape, but it also retains some primitive traits, such as a large canine tooth and a thin enamel. Some researchers have suggested that this jawbone belongs to an early form of Homo habilis, the earliest widely accepted Homo species. In contrast, others have argued that it represents a transitional form between Australopithecus and Homo or even a separate genus altogether.

Another contender for the first “Homo” is Kenyanthropus platyops, a species known from a single skull (KNM-WT 40000) and some fragments found in Kenya and dated to about 3.5 million years ago. This species has a flat face and small molars, considered derived features in Homo, but it also has a small brain size and a long upper face, which are primitive features shared with Australopithecus. Some researchers have proposed that Kenyanthropus platyops is more closely related to Homo than Australopithecus and may represent an early branch of the Homo lineage. Others have challenged this view, suggesting that Kenyanthropus platyops is either a distorted specimen of Australopithecus afarensis (the same species as Lucy), or a variant of Australopithecus africanus.

A third candidate for the first “Homo” is the maker of the Lomekwian tools, a type of stone tools that are older and larger than the Oldowan tools traditionally associated with Homo. The Lomekwian tools were discovered in Kenya and dated to about 3.3 million years ago. They consist of flakes, cores and hammer stones, which indicate that their makers had some degree of manual dexterity and cognitive ability. However, the identity of the Lomekwian toolmakers is unknown, as no hominin fossils have been found in direct association with the tools. Some possibilities include Kenyanthropus platyops, Australopithecus afarensis, or an unknown hominin species. The Lomekwian tools suggest that stone tool technology may have evolved independently in multiple hominin lineages, or that it may have originated earlier than previously thought.

A fourth option for the first “Homo” is the ancestor of the 1470 fossil (KNM-ER 1470), a skull found in Kenya and dated to about 1.9 million years ago. This skull has been attributed to various Homo species over time, such as Homo habilis, Homo rudolfensis or Homo erectus. It has a large brain size (about 750 cubic centimeters), a flat face and small molars, which are typical features of Homo. However, it also has a long and narrow skull shape and large incisors, which are unusual features for Homo.

Upcoming Skulls with Seth!

Coauthored with the New Bing.

Coming up soon is the next #episode of #SkullswithSeth! On this episode we are going to be examining an extremely precious, and rare fossil, the first partial juvenile skull of H. #naledi yet found! #Leti! The name “Leti” was given to the first partial skull of a #Homo #naledi child that was found in the depths of the #RisingStarCaveSystem, located in the #CradleofHumankind, a #UNESCO World Heritage Site in South Africa’s #Gauteng province1. The researchers have named the child “#Leti” (pronounced Let-e) after the #Setswana word ‘letimela’ meaning ‘#thelostone’1.


It’s going to be great!

Youtube Milestone!

Hey everyone, I have some exciting news to share with you! I’m close to reaching 2,000 subscribers on my YouTube channel, and I need your help. I’m less than 100 away from this fantastic milestone, and I would really appreciate it if you could show some love and support by subscribing to my channel. Trust me, you won’t regret it!

Subscribe here:

Why? Because I have some great new content on the way that you want to take advantage of. I’m talking about fun events, giveaways, collaborations, and more as I expand and grow my channel. You’ll be the first to know about all the awesome things that are coming up, and you’ll also get access to exclusive perks and benefits as a loyal subscriber!

But wait, there’s more! If you subscribe to my channel, you’ll also enjoy my various video series covering all things Paleoanthropology. You know how much I love anthropology, right? I want to share that passion with you and show you how fascinating and fun it can be.

For example, you can watch “The Story of Us,” where I interview famous anthropologists and learn about their research, insights, and stories. You’ll hear from some of the most influential and inspiring people in the field and discover how they got into anthropology and what they love about it.

Or you can watch “Skulls with Seth,” where we examine hominin skulls and learn about their features, evolution, and significance. You’ll get to see some of the most amazing fossils ever found and know how to identify them and what they tell us about our ancestors.

Or you can watch “PaleoFridays,” where we tackle a topic-specific challenge related to Paleoanthropology. Whether making stone tools, recreating ancient art, or testing our survival skills, we’ll have a blast exploring the past and learning new things.

And that’s not all! There are so many more video series that I have planned for you, and I can’t wait to share them with you. Please subscribe to my channel today and help me reach 2,000 subscribers. It would mean the world to me, and I promise you won’t regret it.

Thank you so much for your support and for being part of this fantastic community. You are awesome! And remember: stay curious, stay adventurous, and stay tuned!

Did Homo naledi “Bury” their Dead?

Coauthored with the New Bing.

Did Homo naledi bury their dead? This question has fascinated paleoanthropologists since discovering this new human species in 2013. The fossils of Homo naledi were found in a hidden chamber of the infamous Rising Star Cave System in South Africa, where no other animals or sediments were present. The researchers who made the discovery suggested that this could be evidence of deliberate disposal of the dead by Homo naledi. This behavior is usually associated with complex cognition and symbolism.

However, not everyone agrees with this interpretation. Some critics have argued that alternative explanations exist for how the fossils ended up in the cave, such as accidental falls, floods, or predation. Others have questioned whether Homo naledi had the cognitive abilities to perform such a ritual, given their small brain size and primitive anatomy. (Does Brain Size Relate to intelligence or the ability to form a society?- Learn more).

One of the keywords that has sparked debate is “burial”. This term implies intentionality, respect, and possibly belief in an afterlife. But can we use this word to describe what Homo naledi did? Or is it too soon to make such a claim? What evidence is there to support the use of the word burial?

One way to approach this question is to compare Homo naledi with other hominins known or suspected to have buried their dead. The most obvious example is Neanderthals, who lived alongside modern humans for hundreds of thousands of years and left behind numerous burial sites across Europe and the Middle East. The oldest confirmed burial by Neanderthals dates back to about 100,000 years ago, but some researchers have suggested that they may have practiced this behavior as early as 250,000 years ago. Neanderthal burials often include grave goods, such as animal bones, tools, or flowers, which indicate some form of symbolism and ritual.

Another example is Homo sapiens, our species, who buried their dead in various ways and places throughout history. The oldest known burial by modern humans dates back about 120,000 years in Israel. Still, some researchers have argued that they may have started this practice even earlier, around 160,000 years ago in Ethiopia. Modern human burials also show evidence of symbolism and ritual, such as ochre pigments, ornaments, or art.

A third example is Homo heidelbergensis, a possible ancestor of Neanderthals and modern humans, who lived between 700,000 and 200,000 years ago. There is only one possible burial site attributed to this species, in Atapuerca, Spain, where several skulls were found in a pit with stone tools. However, this site is controversial, and some researchers have suggested that it could be a result of cannibalism or natural accumulation rather than intentional burial.(Some, such as Prof. Chris Stringer argue the H. heidelbergensis should be now referred to as a “Basal Neanderthal”, or the species that eventually turned into Neanderthals, and shared extremely similar features.)

Based on these examples, we can see that burial is not a simple or straightforward concept. It can vary in location, frequency, style, and meaning. It can also evolve within the same species or culture over time and space. Therefore, it may not be appropriate to apply the same criteria or expectations to Homo naledi as we do to other hominins. Instead, we should try to understand their behavior in context and perspective.

What significance does this have for Paleoanthropology? The discovery of Homo naledi has challenged many assumptions and stereotypes about human evolution. It has shown more diversity and complexity among our ancestors than previously thought. It has also raised new questions about the origins and development of human cognition and culture. By studying Homo naledi and their possible burial practices, we can learn more about what makes us human and how we became who we are today.

What is the future of Exploration in the Field of Paleoanthropology…according to a chatbot?

Hello everyone! This is me, Seth, a human, I want to make that clear, and I want to make it clear you will always know when it is I, the human, versus one of the many new chatbots that the worlds tech companies are pushing to the market well before they are ready. But, the reason I bring it up, is because I will be using AI to write some content, but only for contents sake. Any real research, coverage, or meaningful content will be created by me, as it always has.

For the fun of it though, I will sometimes do what I am about to, and that is ask Chatbots, in this case Googles “Bard”, and Microsoft’s “New Bing”.

The question that I posed was simple, “Write me a 1000-1500 word blog post on the future of exploration within the field of Paleoanthropology”

Here is what Bard had to say:

“Paleoanthropology is the study of human evolution through the analysis of ancient fossils and artifacts. It is a fascinating and ever-evolving field, with new discoveries being made all the time.

In recent years, there has been a renewed focus on the exploration of the human past. This is due in part to the rapid pace of technological advancement, which has made it possible to extract more information from ancient remains. However, it is also due to the growing awareness of the importance of understanding our evolutionary history.

There are many challenges that need to be addressed in order to continue to make progress in the field of Paleoanthropology. One challenge is the lack of funding. Paleoanthropological research is often expensive, and it can be difficult to secure funding from government agencies or private donors. Another challenge is the lack of trained personnel. There are not enough people with the skills and knowledge necessary to conduct Paleoanthropological research.

Despite these challenges, there are many reasons to be optimistic about the future of Paleoanthropology. New technologies are being developed that will allow us to study ancient remains in even more detail. And more people are becoming interested in learning about our evolutionary history.

The future of Paleoanthropology is bright. With continued research and exploration, we will learn even more about the human past and our place in the universe.

Here are some specific areas where future exploration is likely to focus:

  • The exploration of new sites. There are still many parts of the world where Paleoanthropological research has not been conducted. Exploration of these areas will likely lead to the discovery of new fossils and artifacts that will help us to better understand human evolution.
  • The development of new technologies. New technologies are constantly being developed that can be used to study ancient remains. For example, CT scans can be used to create 3D models of fossils, which can provide valuable information about the anatomy of ancient humans.
  • The study of ancient DNA. Ancient DNA can be extracted from fossils and used to study the genetic makeup of ancient humans. This information can help us to understand how different populations of humans evolved and how they interacted with each other.
  • The study of ancient microbiomes. The microbiomes of ancient humans can be studied by extracting DNA from fossils and analyzing it. This information can help us to understand how the diets of ancient humans affected their health and how they interacted with their environment.
  • The study of ancient cultures. The artifacts that are found in Paleoanthropological sites can be used to study the cultures of ancient humans. For example, tools can be used to learn about how ancient humans made a living, and art can be used to learn about their beliefs and values.

The future of Paleoanthropology is exciting. With continued research and exploration, we will learn even more about the human past and our place in the universe.”

Pretty cool, and interesting huh? But can you see where some of the dangers lay in relying completely on AI generated content for your information?

Here is what Bing had to say,

“Paleoanthropology is a fascinating field of study that has been around for centuries. It is the study of human evolution and the development of early humans. The field has come a long way since the early days of discovery, and it continues to evolve as new technologies and techniques are developed. In this blog post, we will explore the future of exploration within the field of Paleoanthropology.

One of the most exciting developments in the field of Paleoanthropology is the use of 3-D scanning technology. This technology has revolutionized the way that fossils are studied and analyzed. With 3-D scanning, researchers can create highly detailed digital models of fossils that can be studied in great detail. This technology has allowed researchers to study fossils in ways that were previously impossible, and it has opened up new avenues of research.

Another exciting development in the field of Paleoanthropology is the use of DNA analysis. DNA analysis has allowed researchers to study the genetic makeup of early humans and to better understand how humans evolved over time. This technology has also allowed researchers to study the relationships between different species of early humans and to better understand how they are related.

In addition to these technological developments, there are also many other exciting developments in the field of Paleoanthropology. For example, researchers are constantly discovering new fossils that shed light on the evolution of early humans. These discoveries are helping researchers to better understand how humans evolved and how they adapted to different environments.

Another exciting development in the field of Paleoanthropology is the use of new techniques for dating fossils. These techniques are allowing researchers to more accurately date fossils and to better understand the timeline of human evolution. This is helping researchers to better understand how humans evolved and how they adapted to different environments.

Overall, the future of exploration within the field of Paleoanthropology is very exciting. With new technologies and techniques being developed all the time, researchers are constantly discovering new things about the evolution of early humans. As these discoveries continue to be made, we will gain a better understanding of our own evolutionary history and how we came to be the way we are today.

I hope this blog post has been informative and has given you a better understanding of the future of exploration within the field of Paleoanthropology. If you have any questions or comments, please feel free to ask!”

And there you have it! That is what the current iteration of chatbots think about the future of exploration within our field. But is it correct?

Where do you think think the field is going?

Are Neanderthals our Ancestors? A Quick ChatGPT Analysis

Here is what ChatGPT says about “Are Neanderthals our Direct Ancestors?”

I need to write a paper about how Neanderthals are not our direct ancestors

Many people have a misconception that Neanderthals are our direct ancestors or early members of our own species Homo sapiens. However, this is not true. Neanderthals are actually our cousins, who evolved from a common ancestor with us about 600,000 to 800,000 years ago.

Neanderthals were a distinct species of human, known as Homo neanderthalensis, who lived in Europe and Asia from over 200,000 years ago until less than 30,000 years ago. They had some unique features that adapted them to cold climates, such as a large nose, a robust body and a large brain.

Neanderthals were also capable of making tools, using fire and burying their dead. Some evidence suggests that they may have had some form of culture and religion as well. They were not primitive or stupid as some stereotypes suggest.

However, Neanderthals did not give rise to modern humans. Our species Homo sapiens originated in Africa during the last 250,000 years from non-Neanderthal ancestors. We spread from Africa during the last 60,000 years and replaced other human lines such as the Neanderthals.

How this replacement happened is still unclear. It could have been due to conflict or competition for resources. It could also have been due to environmental changes or diseases that favored us over them.

What is clear is that Neanderthals and modern humans did interact and interbreed on some occasions. This is evident from the fact that some people today (particularly in Eurasia) have traces of Neanderthal DNA in their genomes.

However, this does not mean that we are descended from Neanderthals. The amount of Neanderthal DNA in modern humans is very small (less than 4%) and does not affect our physical appearance or behavior significantly.

Therefore, we can conclude that Neanderthals are not our direct ancestors but rather our distant relatives who shared a common history with us for a brief period of time.