Category: Human Biology

The Importance of Turkana Boy

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Turkana Boy or KNM-WT 15000 was discovered in 1984 by Richard Leaky’s team in Kenya. He would prove to be a very important find, being around 40% complete having most of its skull, long bones and hips. And bases on his osteology I would say that him and Homo erectus where not that different from us the neck down, and explain his species importance to us. Here is why.

Neck down he had a body plan that was almost exactly like our. He was only around eight or nine when he died but based on the bones and teeth the species had a slightly faster growth rate then us. But even at eight he was around 5 foot 3 and still growing. His hips where shaped like ours and he also had long legs and shorter arm like us suggesting that he was completely bipedal and his species being adapted completely to the  ground. Fossilized footprints from another member of his species dates back around 1.5 million years ago proving that they had a similar gait and stride to us and that they were capable of long distance walking and running.

Based on Turkana Boy they also had adapted to the very dry hot climate of East Africa. He had a narrow slender body with long legs and arms. This reflects what is called the Bergman Allen rules. Which can be seen in, especially mammals, species around the world. The hotter dryer environment to help dissipate heat its better to have longer limbs(Allen) and slender shoulders and hips(Bergman). You can still see this in modern day humans living in the opposite extreme environments like the Inuits of North America or the aboriginals of Australia.

I can also make some assumptions about their physiology. I think Turkana Boy and Homo erectus had the adaptive cooling mechanism to sweat. Sweating had to of originated in the hot dry environments of Africa. This type of cooling mechanism doesn’t make sense in a hot humid environment because there is to much water in the air already for sweat to evaporate efficiently to get rid of heat. It defiantly doesn’t make sense for it to originate in a cold environment. His long limbs also reflect that with longer limbs means more sweat glands and ability to effectually stay cool in a very dry environment. And if they had sweating as a cooling mechanism they would also have been hairless one the body similar to today. Because for sweating to work there skin would need more exposure to the sun so sweat can effectively evaporate taking heat with it. One last assumption, if they were sweating and had less body hair their skin would need protection from the sun and they mostly likely had abundant amount of melanin. And with this strong selective pressure to be protected from the intense UV rays of the sun they would have had dark skin.

To modern day we are still very much bipedal. We are still the “hairless apes.” And even though I don’t like it on a humid Midwestern summer day we are also still able to sweat which might have all started with our ancestors like Turkana Boy.

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Mitochondrial Eve

The title might be a little misleading for it doesn’t show the first woman in our species, but the most recent mitochondrial ancestor of all humans and everyone today is a decedent from her. But what is mitochondrial DNA? It’s separate DNA outside of the nucleus that located in, you guessed it, the organelle mitochondria. And it doesn’t recombine like nucleic DNA so when it is pasted down through the generation it undergoes very little change. The way mtDNA works is it’s pasted through the maternal line given to daughters and sons, but the her sons significant other will only pass down mtDNA to there children from her own maternal line.

But why is there DNA in mitochondria in the first place? Well it goes far back when there was only single celled organisms and instead of digesting smaller bacterium these single celled organisms made a symbiotic relationship where instead of being digested were copied in the cells reproduction cycle and the first mitochondria where small bacterium. The theory that explains this endosymbiotic theory that is accepted by most scientists today.

MtDNA also lead to whats is called haplogroups, which can look at your ancient ancestry as well as migration of past human populations. The way it works is people in a haplogroup can trace that specific mtDNA to a common ancestor. The changes in mtDNA are created by a mutation and each of these changes in the mtDNA is a different haplogroup.  Not everyone has the same mutations in the mtDNA because these mutations happened in different geographical locations at different times. And using mtDNA and archaeological evidence it can be used to track human migration. One example is a person in Northeast Asia can have the same haplogroup found in Native Americans showing a common ancestry among them that created that haplogroup in Asia. And around 15,000 years ago people in Asia migrated to Alaska with the same Haplogroup.

But since mtDNA shows a portion of ancient ancestry you most likely wont find a lost family member if you learn a stranger has the same haplogroup as you since haplogroups origins can be thousands of years old.

 

https://blog.23andme.com/23andme-and-you/haplogroups-explained/

 

Smaller Brains

For most of human evolution there has been about a 2 million year anatomical-reflectiontrend for bigger brains. But in the last 20,000 years there has been quite a reversal on that ancient trend.  And I’m not pulling a fast one on you, for a time this was only a known fact among paleoanthropologist, and they notice this trend despite what region of the world or demograph. And when biologists and geneticists learned about this trend they were as surprised as anyone that our specious are loosing grey matter. It does make sense though that anthropologists specifically paleoanthropologists would recognize this trend since they are likely the only field that looks at contemporary human anatomy to millions of year old fossils and skulls.

Based on skeletal analysis of skulls from 20,000 years or before the average volume of someones brain was around 1500cc (cubic centimeters) and today that has dropped to around 1350cc. That’s about the size of a tennis ball! And as I said this trend is happening everywhere, Europe, Asia, Africa you name it. Simply put by anthropologist Christopher Stringer “It’s Strange.” And for now no one really knows why this trend started or whether a smaller brain is inherently bad or will lead to less intelligence. But there are some studies that are trying to understand this trend.

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One studied suggest that the development of complex societies lead to a decrease in brain size. As society became more complex and spread the workload there was no need for a big brain to us your wits and try to survive. Civilization became like a social safety net.

One study measured the skulls of Europeans from the Bronze age around 4000 years ago to the medieval times. This research got similar data that as populations increased and society got more complex the trend of smaller brains continued. But the study suggest a smaller but smarter brain. Because a bigger brain takes so much energy to keep functioning, it already takes up about 20% of all calorie intake. So the goal is a smaller but smarter brain. And over the past 20,000 years there have been adaptive mutation related to brain development and neurotransmitter systems that changed the inner working of our brains, but to what extent no one knows. Though they could have affected our temperament and reasoning abilities.

One Study states that it isn’t to do with intelligence but rather the selection against aggression. And that in a way we domesticated ourselves or became more tame. Like all the other animals we have domesticated their brain size has gotten smaller and so more tame than there wild counterpart.

But so far we can only see the changes of our evolution but not where it’s taking us. By anthropologist Stringer “it’s perfectly plausible our modern brain is smarter in some ways, dumber in others, and more docile overall.”

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For more information:

http://discovermagazine.com/2010/sep/25-modern-humans-smart-why-brain-shrinking

Remnants of the Past

Our bodies are literally littered with our ancestral past. And for a time people couldn’t explain why we had certain traits that were either very odd or served no purpose. Starting in the 18 hundreds  paleontologists and biologists were beginning to explain and examine these enigmas. Today biologists and physical anthropologists explain them as either vestigial structures, atavism, or pseudogenes.

Vestigial Structures:                            img62

Vestigial structures are like souvenirs of the past, more specifically our evolutionary past. These traits are being expressed in the body but have no use or a use that does not reflect its original function/adaption to be used for its original purpose. This reflects that all organisms have a common ancestry and certain groups share a common descent . This also reflects divergent evolution, which means different groups of animals with a common ancestor adapt to the variety of environmental conditions. And as other features of our body become less important for the environment we live in, they might eventually become a vestigial organ.

Appendix

The apendix is a small organ left over from when our ancestors had a largely plant diet. The organ was critically important for breaking down cellulose ( fiber). But now in humans it has become so small, compared to animals like cows, that it has no role in the digestion system, and some people are even born without one. The appendix has even become dangerously small that one in fifteen people will suffer from appendicitis, which left untreated can become life threatening. But whether or not the organ is good or bad it is still a vestigial organ for it doesn’t perform its original function. The organ may even be on its way out but with modern medicine and surgery to treat appendicitis the natural selective pressures have mostly been taken away from people with appendixes.

Coccyx

The coccyx or tail bone, hint hint, is our vestigial tail. Our coccyx is now composed of seven tightly fused bones connected to the end of the vertebrae. It does still have some function, being used for useful muscle attachment for our bipedal locomotion, but remember it’s still a vestigial structure because it no longer has its original function it was evolved for. Some people are even born with a rudimentary tail muscle that is attached to the coccyx. It is also identical to other animals that have a tail. But since the coccyx doesn’t move the muscle is useless. You may be sitting on it and not even notice!

Arrector Pili   arrector-pili-muscles

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Ever see a scary movie and get goosebumps? Goosebumps are created by the muscle arrector pilli that is attaches to your body hairs. The muscle is useless now in humans because we also have vestigial body hair. But the original purpose is to raise fur to create heat and insulation and to express behaviors to look bigger and also warn off predators.

Ear muscles

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If you can wiggle your ears you are demonstrating a vestigial trait. These are the same three muscles attached to animals like cats or deer, used to locate sound to protect them from predators and so on. But there was a evolutionary trade-off that began with our ancestors to have color and stereoscopic vision( helpful in trees) , sacrificing good sense of hearing as well as smell.

Atavisms:

A human embryo were during development a “turned off” gene can be re-expressed.

On rare occasions an individual will have a anomaly that looks like the reappearance of an ancestral trait. To have a atavism it must be the re -expression (gene expression) of a ancestral trait. For example someone with an extra limb does not have an atavism because none of our ancestors have five legs. But why do atavisms occur? It comes from the re-expression of genes that was once functional in our ancestors but then “turned-off” by natural selection when they were no longer needed. Yet these silenced genes in our genome can be be “turned on” again when something goes askew in development.

Human Tail people-with-tails2-624x1110

The most striking atavins in our own specious is the human tail. Human tails are true atavisms because we carry exactly the same gene to make a tail also found in other animals. We actually had a tail when we were just an embryo, but after seven weeks of development these genes are deactivated from further growth and the tail is reabsorbed by the body. But rarely the genes aren’t “turned off” and we have people with tails.

Pseudogenes              6b900d6d15b4c152557b8d11a94457bf

To continue with the ‘turned off” genes, scientists have discovered that in humans and other animals there are loads of genes that are no longer “tuned on” or expressed (gene expression). These genes that are no longer functioning are called pseudogenes. Essentially they are like vestigial genes for they don’t function the way they were once evolved to do.

Vitamin C

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The 2 GLO gene structure shows the independent mutations of two mammalian lineages that lost the ability to produce Vitamin C.  This also shows that the two separate lineages have a common ancestor.

A popular example of pseudogenes in humans and all other anthropoid primates is our inability to produce vitamin C. Vitamin C is essential for a healthy metabolism, and virtually all mammals produce all the vitamin C they need. But not anthropoid primates and some other mammalian lineages like the guinea pigs, and fruit bats. And the reasons why we don’t produce vitamin C is because we obtain enough from our diet being able to eat and digest vitamin C from fruit. Yet in our genome we still carry the mutated  pseudogene GLO which creates the enzyme to produce Vitamin C.  Shows that vitamin C synthesis is also an ancestral trait of mammals and that this trait has been lost in three mammalian lineages: bats, guinea pigs and anthropoid primates.

A Video about vestigial structures hosted by a funny guy Hank Green who talks a lot about science in the YouTube channel SciShow.

First blog post

First blog post

Anthropology. What? anty-banner

Most people will go through life without understanding anthology, or even talk to an anthropologist. So, people can have a vague idea what anthropology is. Some will automatically think Indiana Jones, when he was an archaeologist and a bad one at that. Though I do like the hat. Or say yeah, I like bugs to, hearing entomology instead of Anthropology. For those and many other reasons I decided to write this blog post about what Anthropology is and its origins.

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Around the time explores made transcontinental travels they made amazing discoveries in new lands that help us further understand our world in fields like natural history, geology, and biology. But when the explorers got to “new” lands they encountered people as well. People that looked, talked, and dressed very differently from there way in western society. And in an age of great discovery and further understanding Europeans tried to explain this, what was to them, phenomenon. And slowly but surely the discoplone Anthropology was born in the 19th century. Even when you look at googles “use over time for: anthropology” graph the word catapults from 1850’s to modern day.

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Frank Foas. Considered the “Father of American Anthropology.”

Anthropology in America will eventually be known as the study of humankind, viewed at all perspectives of people at all times. American anthropology has become so specialized, we can also look at ourselves in many different but connected ways, it has been divided into four sub-fields. The four sub-fields in America are Cultural anthropology, archaeology, linguistics, and physical(biological) anthropology.

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Margaret Mead. A popular Cultural Anthropologist. With a mother in the Admiralty Island

Cultural Anthropologists studies living cultures and will often spend long trips with cultural groups to gain more intimate perspective of these cultures. Archaeologists are like Cultural Anthropologists, but study the past cultures using material culture or more known artifacts. Linguists study language, its structure, evolution, and social and cultural context for language. Finally, physical anthropologists study the human evolution and variation, both past and present.

Even through anthropology is very diverse it is also a studying field that holistic as well. Unlike other disciplines, anthropologists study humans using a biocultural approach. Acknowledging the fact that there is a intercorrelation between culture and biology using scientific study.

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Louis and Mary Leaky. Famous Paleoanthropologists in East Africa (successfully) looking for hominid fossils.

Now I will only be blogging about Physical Anthropology and its fields. If you think looking at one fourth of the sub-fields will be a light read, then you’re wrong. What makes physical anthropology interesting is its relationship with the other sub-fields and that it is science and social science. Also, its close ties to other disciplines like biology, genetics, paleontology, geology, and many other fields and specialties. So, I hope you enjoy my topics but more so the world that is Physical Anthropology.