Join us on a Journey through Deep Human Time…
Wow, we made it halfway through season two already that is crazy. George and I can’t believe how much we have learned and grown from each other over this small time and can’t wait for what this future holds for this podcast and for all of you!
Cheers! Be sure to listen to the episode!
Vingen Rock Art at Risk, The First Art Team and what you can do!
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Hello everyone! I have something that I am excited and would like to share with you! A professor by the name of Dr. Michael Petraglia et. al have formed a new group of exceptional researchers and scientists to take a deep dive into our shared Human Journey.
In the ever-evolving tapestry of human history, the future holds untold wonders and possibilities. Among the many threads that weave together the fabric of our existence, understanding our origins stands as a beacon of enlightenment, guiding us toward a brighter tomorrow. The Human Origins: Our Future organization serves as a testament to the profound significance of delving into the depths of our past to shape a future filled with promise.
“The International Initiative for Human Origins and Our Future will seek to decentre human origins research by integrating Indigenous, Global South and other international perspectives into the study of human evolution. With well-developed legislation and practice surrounding cultural heritage, Indigenous rights to heritage, and the use and ownership of cultural knowledge, Australia leads the way globally in efforts to overcome colonial legacies of archaeological research”
Our species, Homo sapiens, has traversed a remarkable journey spanning millions of years, leaving behind an intricate mosaic of cultural heritage and scientific knowledge. By embarking on an exploration of our origins, we unlock a treasure chest of insights into the essence of our humanity. The intricate tapestry of our past reveals the threads that connect us to one another, offering a glimpse into the forces that have shaped our societies, cultures, and beliefs.
The Human Origins: Our Future organization stands as a beacon in the vast sea of information, illuminating the diverse facets of human evolution with remarkable clarity. From the earliest hominins who walked the Earth to the emergence of modern humans, the organization weaves together a captivating narrative that chronicles the extraordinary saga of our species’ remarkable journey. Each chapter unfolds with the vibrancy of a well-crafted story, engaging the reader in a quest for knowledge and understanding.
Moreover, the organization recognizes the indispensable role of interdisciplinary research in unlocking the mysteries of human origins. By fostering collaboration among archaeologists, geneticists, anthropologists, and other experts, we gain a panoramic view of our past, integrating diverse perspectives to create a more comprehensive tapestry of human history. This collaborative approach allows us to uncover hidden connections, challenge long-held assumptions, and gain a deeper understanding of the intricate forces that have shaped our species.
The true power of the Human Origins: Our Future organization lies in its ability to bridge the chasm between academia and the general public. It presents complex scientific information in an accessible and engaging manner, making it a valuable resource for students, researchers, and anyone with a thirst for knowledge. Through interactive multimedia, captivating storytelling, and thought-provoking discussions, the organization invites visitors to embark on an intellectual journey that will leave a lasting impact on their understanding of the human experience.
As we move forward into an uncertain future, the Human Origins: Our Future organization will remain a vital platform for knowledge sharing, collaboration, and innovation. By nurturing a deeper understanding of our origins, we can embark on a path of progress, embracing the potential for a brighter and more sustainable future for humankind. The organization serves as a reminder that the seeds of our tomorrow are sown in the soil of our past, and by cultivating a profound understanding of our roots, we can shape a future that is worthy of the remarkable legacy of our ancestors.
Please do check out the website, and their sites across social media, and be sure to keep an eye on them, as I expect so much to come from this great idea!
Seth
Yesterday I had the absolute honor of chatting with the President of the AABA and researcher at the Spanish Institute CENIEH, which is a consortium dedicated to the understanding of Human Origins in Europe and beyond, particularly working on the site of Atapeurca, which is an extremely important Paleolithic site. One which as been investigated for years, and more and more keeps coming out!
Have you heard of naledi and the “Cave of Bones”? Well Atapeurca is the “Pit of Bones” and in many aspects is as interesting, if not more so than Rising Star. But that will all be for a later episode! Possible on the PaleoPost Podcast, so be sure to check that out and stay up to date with that!
Dr. Hlusko and I talked about her route to where she is today, and her advise to anyone who wants to follow in her footsteps. We talk her main projects, (which are super cool and she does a great job of explaining them) and we talk of course about the AABA, and the conference coming at the end of next month in Los Angeles!
It was a blast, and while I know you will learn something, show me that you have by leaving a like, or subscribe if you have not already to get more content just like this, and so much more! It really helps out the channel!
Thanks
Catch it here:
Introduction
Throughout the history of our evolution, there have been many different things that have shaped us into the animals we are today. From mutations to selection pressures, there are many aspects of our story that are crucial for why we are the way that we are, both behaviorally and physically. This article is about the latter.
Despite being so closely related to our ape cousins, we physically look quite different in a few ways, especially in our skulls. The other apes, especially the great apes, have very large projecting (prognathic) faces, large brow ridges, larger teeth (especially in the canine teeth), and especially, small brains. Humans however, have flat faces, no brow ridges, small mouths and teeth, and very large brains, the complete opposite. What little genetic difference we have with chimpanzees makes up for all these differences.
There is one overarching reason for this, why we look so different from the other apes despite being so closely related to them, and it requires very little genetic difference. It is called neoteny.
What is Neoteny?
Neoteny is a biological phenomena that has been observed in many different animals, including, it seems, humans.
Neoteny is broadly a form of heterochrony, which is a change in the timing of growth stages in an organism. More specifically, neoteny is a form of paedomorphism, which basically means to have a more juvenile-like appearance. Neoteny specifically is the retention of juvenile traits into adulthood. This usually happens when a mutation causes sexual maturation to occur sooner, when the individual is phenotypically younger. That specific form of neoteny is called paedogenesis. Neoteny is a form of paedomorphism, which is a form of heterochrony.
Neoteny can be very important for evolutionary changes, as if the retention of a certain trait is beneficial, it’ll be passed down, causing great evolutionary changes. Ontogeny is also another important topic for understanding neoteny.
Ontogeny is the development of an organism throughout its life. As neoteny is the slowing of development, ontogeny is important to understand when discussing this topic.
Examples of Neoteny
There are many examples of neoteny in animals. Many dog breeds have been selectively bred to be more neotenic. Younger wolves are more social and friendly, making them better household pets, rather than more aggressive guarding and hunting dogs like they were originally domesticated for. This resulted in humans selecting for wolves with more puppy-like behaviors.
Physical neotenous traits were also selected for. Neotenous traits seen in some dog breeds include softer fur, rounder bodies and heads, larger eyes, and floppy ears.These traits are often seen as cuter and friendlier, making them more popular among dog owners. Unfortunately however, these traits are often unhealthy for the dogs, as many have congenital issues, such as brachycephalic skulls, making breathing difficult.
Dogs with these neotenous traits include breeds like chihuahuas and pugs. Dogs were artificially selected for, but there are many natural examples.
Neoteny is also seen as the reason why naked mole rats (Heterocephalus glaber) have such longer lifespans.
While some rodents, like mice, have an average life span of 3 years, naked mole rats can have life spans of up to 30 years. Neotenic traits in these rats include a lower body rate, lack of hair, prolonged gestation, longer times to reach maturity, greater percentage of reproductive success, the absence of a scrotum, a reduced vomeronasal organ, etc. Very few other rodents have these same traits into adulthood.
At birth, naked mole rat brains are much more developed than other rodents as well, and are more alike that of newborn primates. Despite this, these rats take much longer for their brains to mature, taking 4 times longer than average for other rodents. This is a sign of increased neoteny in the brains of these rats.
Another good example of neoteny is the mexican axolotl (Ambystoma mexicanum).
Axolotls are one of few amphibians that don’t undergo metamorphosis. Because of this, they retain many juvenile traits throughout their lives. One of the most outstanding traits is external gills, one of their most distinguishing traits.
This paedomorphosis is a result of low activity in the hypothalamo-pituitary-thyroid (HPT) axis. The pituitary hormone thyrotropin (TSH) is capable of inducing metamorphosis in axolotls, so all functions of the HPT axis (metabolism and stress responses, etc.) below the pituitary level are functional, except this TSH release.
Neoteny in Humans
There are many examples of neoteny in humans as well, which have had big impacts on our own evolution. Neoteny, especially, is common in our brains. Because of neoteny, our brains take much more time to develop, allowing us to learn much more as we develop. This gives us time to learn more complex behaviors and learn from environmental cues. Extended development in the brain is primarily due to mutations on important developmental genes in the brain.
The slowing of the development of the amygdala-medial PFC (prefrontal cortex) allowed for more time for children and parents to bond. This part of the brain is important for emotional maturity, in behaviors like attention, learning, modulation, and prediction, so extending its development is very useful.
When compared to the brains of other primates, specifically chimpanzees (Pan troglodytes) and monkeys like rhesus macaques (Macaca mulatta), humans have much more extended brain development due to this.
When the human variant of the MCPH1 gene, another important gene in brain development, was placed into rhesus macaques, the monkeys experienced greatly delayed brain development, and subsequently exhibited better short-term memory and shorter reaction time when compared to unaltered monkeys, just like what is seen in humans. This shows that the human variants of these genes, which are important for our memory and reaction time, have been greatly changed in our lineage compared to our cousins.
Other genes that control brain regulation, such as RBFOX1, an important hub gene in brain development, are very different from rhesus macaques, showing just how much the human brain has changed in terms of development.
In total, about 7,958 genes related to brain development have been compared between humans and other primates. About half of these genes possess delay in development in humans. Out of 299 of those genes, 40% are even expressed later in our lives than in other primates. This delayed maturation of the brain also has behavioral impacts.
With a larger, more mature, more self aware brain, human social interactions have become much more complex. This may have increased levels of shyness, both fearful and self-conscious shyness.
There’s another neotenous change in humans that is important for human brain development, but rather than the development itself, it’s important for the size of human brains.
Compared to other apes, humans have much smaller jaw muscles and larger brains. This is the opposite in our ape cousins. However, as juveniles, other apes have larger brains and weak jaw muscles, just like humans. This changes greatly as the other apes develop throughout their lives, but it remains this way in humans. This is due partly to a single mutation on one important gene, MYH16.
The MYH16 Gene
MYH16 is a gene found in mammals, but specifically is used in the temporalis and masseter muscles in primates, muscles that are important for chewing.This gene codes for a myosin heavy chain protein, an important protein for muscle contractions in the jaw muscles.
Though this reduced our chewing muscles and therefore our jaw size, it allowed for an increase in brain growth (encephalization), and was therefore beneficial. In humans, this gene has been converted into a pseudogene due to a two nucleotide deletion mutation, hindering the production of the MYH protein, and reducing our chewing muscles. Though this reduced our chewing muscles and therefore our jaw size, it allowed for an increase in brain growth (encephalization), and was therefore beneficial.
Because humans are such social animals, having a larger and more mature brain is very beneficial. We traded our brains for our brawns. This is known as the “less-is-more” hypothesis, having less chewing muscles is more beneficial.
This mutation would have occurred anywhere from around 5.3-2.4 million years ago, likely closer to the latter. It occurred after the split between chimpanzees and humans, but before the split between modern humans and Neanderthals.
This is why chimpanzees and humans look so different in their skulls, despite both being more closely related to each other than either is to a gorilla, because a single mutation alters the growth of chewing muscles in humans, allowing for a larger brain. The roughly 1% genetic difference between chimpanzees and humans is a big difference, partially due to this mutation in this singular gene.
This is neotenous as smaller chewing muscles and larger brains are present in the juvenile forms of all apes, but goes away in all but humans, where it is retained. This is where ontogeny comes in.
Human and Ape Ontogeny
Humans are most similar to the other apes as fetuses, and their skull shape soon begins diverging slowly after birth. Some of these changes diverge at the same rate, while other traits diverge at different times and at different rates.
Some of the biggest changes during ontogenetic development are in the face. Other, non-human apes obtain a larger, more prognathic face, larger teeth (especially in the canine teeth), and a smaller brain. Other important changes include changes in the basicranium, specifically in the foramen magnum. This is important for the locomotion of the animals later in life. These changes are in the neuro and splanchnocranium, the two major portions of the skull.
The splanchnocranium succeeds the neurocranium in the development of the endocranium (the inside of the skull). These changes occur at similar rates in other apes, but are very different in humans, though some variation does exist. Because our brain development is so different from the other apes, there are also other ontogenetic changes in the human endocranium, although ontogeny isn’t the only reason for this.
The brains of postnatal humans begin growing very rapidly. By year one, the brain is 70% the adult size, and by year 6, it’s 90-95% its adult size. Due to the smaller sizes of the brains of other apes, this is very different in them. Humans have an increase in endocranial flexion (pushed forward occipital bones) compared to other apes as well, which is important for some of the other ontogenetic between humans and apes. Cranial flexion also helps with spatial packing of our larger brains, along with aiding in bipedal locomotion.
Some major endocranial changes we know have occurred very recently in our species, as early fossils of our species, like the Herto cranium, lack them, showing that they’re very new traits. The Herto skulls, despite being only about 160,000 years old, have a very different endocranial shape from modern Homo sapiens, though the brains were about the same size.
Due to all these changes during development, the skulls of adult humans are closest to the skulls of juvenile chimpanzees, aside from the growth of the teeth.
The fossils of juvenile australopiths, like the taung and dikika child, are important for tracking these cranial changes in the human lineage. There are also examples of different ontogeny in other places besides the skull. One good example is in the spine, specifically the thoracolumbar region.
The spine anatomy in apes is very diverse, mainly due to posture and locomotion. Because of the different vertebrae throughout the apes, the ontogeny of the vertebrae is unique. Not a lot is known about the development of the vertebrae, but comparing the vertebrae of juvenile humans, apes, and extinct hominins like Australopithecus and Homo erectus.The vertebrae of humans and chimpanzees are more alike than they are to gorillas and orangutans.
Also in chimps and humans, the development of the vertebrae develop much more than in the other apes. In humans however, our development finishes much quicker. This is exactly what is seen in extinct hominin species. Though the vertebrae of humans and chimpanzees are very similar, one big change is humans gain a longer lumber column, which aids in our upright posture. Ontogeny is also present farther down the body in the femora.
Even though chimpanzees and gorillas walk very similarly, the ontogeny of their femora is still different in multiple ways. The basic development of the femora in primates is the same, but varies in slight details. Humans differ from this the most, with longer angled femora, also for bipedal locomotion. Overall, humans most resemble our ape cousins in most aspects of the body when they’re juveniles, but this quickly changes as the other apes grow, while humans stay relatively the same.
Conclusion
Evolution is run primarily by random mutation, which is then selected for by non-random mutation. Depending on what the mutation does, and the environment of the organism, the change will either be selected for or selected against. Humans, up until very recently, have been exposed to countless selection pressures. As a very social species, having a mutation that allows for extended brain development and an overall larger brain would be very quickly selected for. Neoteny is one of the many ways this occurred.
Neoteny allowed us to trade our larger mouths and stronger bites for larger brains and extended brain development. This is why humans look so different from our closest living relatives. There have been a few small genetic changes in a very small portion of DNA that drastically altered our lives, biology, and appearance, showing just how significant small genetic changes can be.
Sources
Did Human and Neanderthals Share Art Tips? What we know about Human-Neanderthal Interactions!
be sure to watch the latest episode of the PaleoPost Podcast to hear what it might mean that modern humans and Neanderthals interacted for millennia?
Did we learn how to make art form them? Or did they pick up tips from us?
The mystery deepens on this episode!
Introduction
One of the most important, if not the most important concepts in modern biology is evolution. The idea that organisms change with time and are all related back to a common ancestor was revolutionary, and important for understanding pretty much every aspect of biology. The history of the theory of evolution was long and complicated, and evolutionary thought had been a thing for hundreds of years, but perhaps the most revolutionary thinker was Charles Darwin, who was born on this day, February 12th, 215 years ago.
Darwin’s Early Life
Charles Robert Darwin was born in Shrewsbury England on February 12th, 1809. He was born into a wealthy family with 5 siblings, with his father and mother, though his mother died when he was young. On his fathers side, there was a history of scientists, with his father, Dr. R. W. Darwin being a medical doctor, and his grandfather, Erasmus Darwin being a well known botanist.
His father hoped his son would go down the path of medicine as well, but Darwin was more interested in natural history. After graduating from Christ’s College in 1831 with a bachelor degree of arts, a botany professor, John Stevens Henslow, recommended Darwin take a naturalist’s position on the HMS Beagle, a trip that would not only change his life, but would change the history of science as a whole.
The ship, captained by Robert Fitzroy, embarked on its 5 year journey in December of 1831 when Darwin was 22 years old. His role on the boat was to study the discoveries made on the journey, but also to provide companionship to the captain.
In total, he spent about 1,200 days on land during the voyage, where he would study many different animals, plants, and fossils. Most famously during the journey, the Beagle spent 5 weeks on the Galapagos islands. It was on these islands where his observations would form his famous theory of evolution by natural selection.
On the Galapagos islands, he studied geology and wildlife. Most famously, he studied the birds of the islands. Though commonly called Darwin’s finches, these birds weren’t actually finches, and were likely more closely related to blackbirds or mockingbirds. Regardless, the observations Darwin made about these birds were crucial for the development of the theory of natural selection.
These birds proved to be an incredible example of adaptive radiation, speciation, and natural selection.
Darwin’s Research and Work
The environmental occurrences on the islands led to a great variation in the birds, such as variation in beak size, body size, plumage, etc.., as they adapted to the different environments of the different islands.
The beaks were some of the most prominent examples, as each bird species adapted to different food sources. The geographic isolation across the different islands led to allopatric speciation, as gene flow between the different populations was stunted.
It wasn’t completely stunted however, as genetic research shows that there was interspecific gene flow across the species, resulting in hybridization, making this a good example of the arbitrary nature of ‘species’.
Genetic analysis also showed the different genes that affected the adaptation observed in the finches. The ALX1 and HMGA2 genes for example have been shown to affect the shape of the beaks across the different species. His observations on the Galapagos, along with his expedition of the Beagle as a whole, inspired Darwin to write On the Origin of Species, one of the most significant works of scientific literature. This book would be published in 1859.
In this book, Darwin proposed his theory of evolution by natural selection, along with the theory of common descent, two crucial ideas in modern biology. This book sparked many, often religious debates, but was more widely accepted due to the evidence and arguments he provided.
Darwin would go on later to publish several other books, including The Descent of Man, and Selection in Relation of Sex. He covers multiple topics in this book, including sexual selection, but more importantly, he addresses the topic of human evolution.
He talks about embryology in the first chapter as a way to study human evolution. In a time without hominin fossils and genetics, he had to pull from what he had.
He made several predictions that would later be proven, such as the idea that humans evolved in Africa, but also made several problematic claims about race and sex, proposing that human social organization follows a straight path from savagery to more advanced cultures.
However, this doesn’t mean that all of Darwin’s views on these topics were wrong.
Most famously, Darwin strongly criticized and disliked slavery, and strongly supported abolition. Darwin was a product of his time, just like everyone is, so it’s understandable that he had views that today we view as controversial today, because they were normal back then. That is how society functions. We cannot critique his scientific theories purely on the basis of these specific views. Rather, we should view them with a critical and most importantly scientific lens, and understand the many things he got wrong and right about evolution.
Conclusion
Darwin would die April 19th, 1882, at the age of 73, in Kent England. He lived a long and successful life, had many kids, and many scientific achievements. His ideas were revolutionary, and much of them we know today were spot on, but not all. He got things right, he got things wrong, but what he got right was incredibly important for our modern understanding of biology.
It is important to note that scientists do not praise Darwin. They did not and do not follow his every word and idea. A good scientist should recognize what he got wrong and right, and understand the significance of his ideas on evolution and the history of life on this planet. Darwin was a normal man, but a man who had many ideas that have been shown again and again to this day to be correct. Happy Darwin Day!
Sources
Unearth the Secrets of Human Evolution with the Paleo Post Podcast:
Ever wondered where we came from and how we got here? Then the Paleo Post Podcast is for you! Join paleoanthropologists Genevieve von Petzinger and Seth Chagi for Season One, and Dr George Nash for Season Two, as they delve into the fascinating world of human evolution, from our earliest ancestors to the modern day.
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Introduction
In the field of anthropology, scientists will look at anything if it can give clues about the story of our evolution. Fossils and genetics of ancient hominins are the most commonly studied things when researching paleoanthropology, but oftentimes, evidence can be found in small, unexpected things. One such thing, surprisingly, is lice.
The 3 species of lice which live off of humans have very interesting evolutionary histories and very interesting, and helpful implications for our evolution. Specifically, we can learn lots about the loss of fur and the later invention of clothing in human history, both of which are very important for understanding our own story.
The Biology of Lice
Lice are small insect ectoparasites which live off of the blood of their hosts, mainly placental mammals and birds. Lice have short lives and have a short life cycle, consisting of an egg, nymph, then adult. Each lice species is specific to their host species, and rarely inhabit multiple species.
They live alongside their hosts, and cospeciate into new species when their hosts due so, though they evolve at faster rates. Lice are very common and diverse, with roughly 550 recorded species. Human head lice are especially common, with prevalences up to 61%. When it comes to genetics, lice are also diploid, and possess 6 chromosomes (5 metacentric and 1 telocentric), and human body lice have the smallest genomes of any lice species.
Lice belong to the taxonomic order phthiraptera. This group is split into two subgroups, sucking lice (suborder anoplura), and the 3 suborders of chewing lice (amblycera, iIshnocera, and rhynchophthirina). Human lice are sucking lice, and are therefore in the suborder anoplura.
There are 3 kinds of lice that live off of humans, head, body, and pubic lice. All 3 have different habitats on the human body, and have different morphology and behavior to match it.
Body lice Body lice are known to cause several diseases, such as epidemic typhus, trench fever, and louse-born relapsing fever. Body lice are also hosts to the bacterial endosymbiont, Candidatus Riesia pediculicola, which can affect humans as well. These diseases have mostly diminished since the 1940s, with the advent of new treatments and medical practices, but are still present in some places. Body lice are common among homeless people in refugee camps, especially in Africa.
How Lice Relate to Our Evolution
The 3 types of lice that live on humans belong to 2 different genera. Head and body lice belong to the genus Pediculus, while pubic lice belong to the genus Pthirus. These 2 genera are sister taxa, and share a common ancestor going about 25 million years ago (25 mya). Head and body lice are also in the same species, Pediculus humanus. Head lice are in the subspecies Pediculus humanus capitis, and body lice are in the subspecies Pediculus humanus humanus.
Human head and body lice are contained within 6 mitochondrial clades, from A-F. Each clade affects different populations of modern, geographically unique humans. For example, clade F lice affects Amazonian peoples. Clade B lice seem to have arisen from Middle eastern people groups, but are found in many other groups as well, showing that later contact with other peoples, such as Native Americans, transferred the lice. Clade A is common throughout Thailand, and clade C is prevalent throughout Central, southern, and northeastern regions of this area. Genetic evidence shows a possible ancient connection between these people groups in South Asia. Other genetic evidence from lice suggests contact between archaic and modern humans.
Pediculus humanus shares their genus with chimpanzee lice, Pediculus schaefii, which is their closest relative, and the lice of platyrrhine (new world monkeys) (P. mjobergi). It is thought that these monkey’s lice were transmitted to them by the clade F Amazonian peoples who share the rainforest with them. Chimpanzee lice are very similar to human head and body lice, sharing 16/17 of their minichromosomes. Genetic studies show that the divergence of human head and body lice and chimpanzee lice took place around 6-7 mya, which lines up perfectly with the common ancestor of humans and chimpanzees.This suggests that when humans and chimpanzees diverged, their lice diverged and evolved with them, adapting to their new hosts in a cospeciation event. Pediculus lice had genetic substitution rates 14% faster than both humans and chimpanzees, and therefore likely evolved and diverged at a faster rate.
Pubic lice however, share their genus with gorilla lice (Pthirus gorillae). These two groups seem to share a common ancestor with each other, going back 3-4 mya, long after the common ancestor between the two, showing that humans got pubic lice from gorillas somehow else. Gorilla lice were likely transferred to a species of australopith.
What We Can Learn
There are several hypotheses for why humans lost their fur. The not widely accepted aquatic ape hypothesis suggests that hominins would wade in bodies of water in the dry season to collect aquatic food sources, such as tubers and shellfish. Under this hypothesis, hominins lost their fur and developed a layer of fat to better adapt to the water.
Another hypothesis suggests that humans lost our fur in turn for more sweat glands. Support for this comes from the fact that humans have more sweat glands than any other mammal. Having lots of fur on our body would not go well with this, and thermoregulation is more efficient without it.
It is also possible that humans lost our fur because of the development of fire. With the development of fire and clothing, there was less of a need for fur to keep us warm at night.
One of the most common ideas is that as hominins began spending more time in the sun, leaving the trees as we became bipedal and becoming more active hunters in the open savannah, fur became much less advantageous. Less fur would reduce heat overload in the new environments hominins were exposed to. However, fur did not seem as big a problem to australopiths.
There were several assumptions made when this hypothesis was proposed however, such as that the temperatures australopiths lived in were at sea level (while they seemingly lived much more above sea level), australopiths were active all day (while they most likely were only active for about 16 hours a day), and that animals don’t take any thermal costs overnight (while in reality nightly temperatures in eastern Africa can get very low, and thus require more fur to stay warm).
It is more likely that major loss of fur occurred later, in later species of Homo, with exploitation of lower altitude habitats. Later species of genus Homo, such as Homo erectus, would have been much less affected, especially at night, due to their evident use of fire or even living in caves which also raises temperature at night. After a climate cooling event about 2.5 mya, hominins could have occupied much lower altitude habitats.
Because these hominins were much more active compared to australopiths (with Homo ergaster even being 50% more energetically efficient than Australopithecus), and were much more capable of traveling long distances, fur would be much less advantageous. Because Homo ergaster and later Homo erectus occupied lower altitude environments and migrated out of Africa very quickly, the loss of overall body hair would have been a useful adaptation for long distance migration into hotter open habitats.
The idea that australopiths lost their fur due to an introduction to a warmer environment ties fur loss to bipedalism, but there may be some valid ties between the two. One idea is that as hominins began losing their fur, their infants could less easily cling to their mothers, requiring them to stand up to be able to carry them. The hair loss that drove this change to bipedalism may have itself been driven by parasites such as ticks or lice. Losing their fur would have made it harder for parasitic organisms to cling to you.
Under this hypothesis, fur loss should have begun somewhere around 5-8 mya, when hominins began walking bipedally. The lack of evidence of tick-borne diseases in hominin paleoenvironments and the lack of a reason for why fur loss would be so beneficial may go against this idea however. Studying the evolution and divergence of human lice however, specifically pubic lice, may give more hints on why humans lost their fur.
Human pubic lice (Pthirus pubis) seem to have diverged from gorilla lice sometime around 3.3 mya. This is too recent for it to be a result of the human-gorilla common ancestor however. Instead of sharing a common ancestor, human pubic lice seem to be directly derived from gorilla lice, suggesting that hominins gained pubic lice from gorillas. This most likely happened due to hominins (most likely Australopithecus or Paranthropus) inhabiting the nests of gorillas, eating gorillas, or some other form of, possibly sexual contact.
As gorilla lice transitioned to living on human bodies, they may have been forced to reside and adapt to nesting in pubic hair once hominins began losing their fur, as it was the only place they could reside in. No other primates have pubic hair to the extent of humans, but it is beneficial in humans as it can show sexual maturity and trap pheromones. As humans lost our fur, pubic hair would have become more noticable and common, giving a more suitable home for pubic lice.
Genetic evidence suggests that the divergence of human pubic lice occured around 3.3 mya, meaning that humans began losing fur around that time and growing more prominent pubic hair, though it was likely not a drastic change yet at the time. Major loss of fur would come later with the rise of the genus Homo.
During the late Pleistocene and into the Quaternary period, the earth saw dramatic rises and drops in temperatures. These changes in temperature resulted in a series of ice ages, including the last glacial maximum, the most recent major climate fluctuation, which started 27,000 years ago (27 kya).
With these drops in temperature, the development of clothing was crucial for the hominins in the region, specifically modern humans and Neanderthals. From 200,000-30,000 kya, Neanderthals lived through several of these glacial periods. The intricate tools and large brains of Neanderthals made them successful hunters, making furs from different animals more accessible.
Animals like mammoths, bears, musk oxen, and deer, would have provided very good material for hide coats which would have kept Neanderthals warm and dry. Animal hides such as those are not easy to study as they degrade quickly, but the oldest stone hide scrapers go back to about 780 kya. These hides may not necessarily have been used for clothing however, as they could have been used for shelter or other purposes.
Later Homo sapiens seem to have advanced off of the early clothing devised by Neanderthals, by creating more intricate systems. One of these systems was lacing furs together with hiding string. This allowed modern humans to create more complex body coverings, which could effectively cover the body, legs, and feet. One of the earliest forms of clothing which arose from this were tunics. Sewing needles were an important invention around this time that would have aided in this.
Early modern humans weren’t the only ones to use sewing needles however, as a sewing needle about 2 and 3-quarters an inch long was carved out of a bird bone by Denisovans, 50,000 kya. This suggests that Denisovans were producing more complex clothing, which would make sense considering that this population lived in Siberia, where clothing would be important for surviving the cold temperatures. This needle is one of the oldest known sewing needles, but after it sewing needles became very common in human populations throughout Eurasia and eventually into North America.
Other forms of body decoration aside from clothing have been used by hominins before clothing was ever a thing however. Individual talons belonging to white-tailed eagles have been found in the Krapina Neanderthal site, Croatia, with modifications that suggest they were used in bracelets or necklaces, from about 130,000 ya. This one of the many examples of early human jewelry.
Studying the divergence of human head and body lice can also give an idea of when humans began wearing clothes.
The body louse (Pediculus humanus humanus) exclusively nests and lays their eggs in clothes, so when humans began wearing clothes, it would have provided new nesting space, allowing them to diverge. The loss of fur in humans would have isolated Pediculus humanus to the head, and they would have further speciated with the introduction of a new habitat, clothing.
Genetic studies show that there was a genetic bottleneck event in Pediculus humanus, likely due to the loss of fur in humans, narrowing their habitat. A large portion of Pediculus humanus living on the head rapidly diversified to take up the newly introduced habitat, which is consistent with post-bottleneck expansions.
Other genetic evidence suggests that head and body lice diverged around 190 kya, and molecular clock analysis shows that at the youngest possible date for the evolution of body lice is 72 kya. This puts the origin of clothing in modern humans at about 190-72 kya.
Conclusion
Lice may be small, annoying, and downright harmful pests, but we can’t rule them out as an important part of our evolution because of this. Despite their small size and obscure, annoying nature, they are very important for understanding our evolutionary story. Two crucial aspects of human evolution, the loss of our fur, and when we began producing and wearing clothes are much more well understood now because of lice, however unexpected and underwhelming that may be.
Sources
https://www.merckmanuals.com/home/skin-disorders/parasitic-skin-infections/lice-infestation
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