Category: Primatology

Gentle Giants of Madagascar

Madagascar is like a look into the past. Because it split from mainland more than a

DINOSAUR, Aladar, Neera, 2000
Lemurs are old but there not That old. Still liked the movie as a kid.

million years ago, the ecology has lived in isolation allowing ancient species to leave descendants up to modern day. It’s because of this isolation that about 90% of all life on of Madagascar’s is endemic. It’s why Lemurs are alive today and not anywhere else on earth because Madagascar lack the suborder Haplorhini( monkeys, apes, and humans) which out competed them millions of years. And the reasons lorises bush babies, and pottos ( suborder Strepsirhini that includdes lemures) survived in pockets around the world is because of there nocturnal lifestyles that allow them to be active at night instead of the other suborder. So, if you ever thought Lemurs and lorises looked ancient you most definitely would have been right. Also because of there time in a evolutionary isolation from the rest of the world Lemurs have become incredible with a lack of predication and ability to take advantage to all the diverse ecosystems Madagascar had to offer. One of the most interesting finds that have stunned paleontologists are a family called the sloth lemurs or Palaeopropithecidae, which I still can’t pronounce.

1bf16142a913dcfeebcc8112e4af82d6
sloth lemurs on the left. Modern day lemurs on the right corner.

They are interesting not because they are related to sloths. Which even to this day I still don’t know why that name stuck. It’s because of there enormous size that no living lemur can compete with. But like modern lemurs based on the fossil record they where extremely diverse. Varying in size and shape, one even having the skull the size of a gorilla and must have weighed a couple hundred pounds. But, for there size these giants

45221b5b5dd74aeba331d5e28918049c
Archaeoindris fontoynontii, the biggest lemur found yet.

dentition shows they all had vegan diets, eating on mostly fruits and leafs. And based on there size and the fossil record there most likely was never a lot of them living at once per generation, but  some of the species did live to only a couple thousand years ago. They most likely where very close to their habitat making them less adaptable to sudden changes in the environments. And there is some evidence of climate change in parts of Madagascar as well as early human settlements in regions that used agriculture to change the environment around them. There is even fossil evidence of these large lemurs with cut marks on their bones, signs of butchery for either their meat or fur. So the extinction of these animals might have been from human of the environmental change but well probably never know.

On a brighter note. A few years ago now there was a discover of sloth lemur fossils found in  Tsimanampetsotse National Park. Some of the finds had complete skeletons which will help to understand more about there anatomy.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Advertisements

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

hissing-kitten-with-hair-erect

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

ear-ly-talent

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

pmc3145266_cg-12-371_f4
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.

A Bite into the Past

Between 4 million to 1 million years ago there was a a very diverse group of bipedal hominins in East and South Africa called the australopiths. There are currently 9 specious of australopiths discovered and several of them lived concurrently at a time. They can be divided into two groups, the more gracile generally having a smaller build and a more generalized diet. While the robust have a tank of a skull that was very specialized for the food consumption in their niche. And based on there teeth between the two groups they had a very diverse diet that most likely varied between species. But what changed in Africa gave rise the the first hominin and would eventually lead to us?

Before 4 million years ago in Africa there were prevalent rainforests with species similar in morphology in the skull and diet to modern day African apes, gorillas, and chimps. Chimps and gorillas spend half of there waking hours chewing on mostly fruits and high fibrous plants. The shape of there molars with thin enamel are used for sheering there food and large canines used to peel the hard exterior of fruit. But by the epoch of the Pliocene(5.3-2.6 million years ago) there was this ongoing trend of the earth becoming cooler which made Africa drier. During the australopiths era, the cooling made wide spread open wood lands and grasslands. Which greatly diminished and scattered limited fruit. This would lead australopiths to a diet of less nutritious diet of leaves, stems, seeds, and also tubers and roots, and bulbs(which were year round and can survive droughts). With the change in the environment and a change in the opportunity of less nutritious foods would have strong selective pressure for adaptations to obtain the nutrients from there varying diet. Also because they had such a varied diet compared to the their ape counter parts, and lived in varying environments creating new niches creating a very diverse (textbook adaptive radiation) radiating genus separated into the two groups of gracile or robust Australopithecus.

Morphology:screen_shot_2013-12-10_at_33801_pm-142dea8f0d254db55af

Because of the hard, less nutritious, and fibrous foods they where primarily eating, unlike chimps in the rain forest, natural selection acted strongly on the components of mastication (chewing) to breakdown foods into smaller particles to easily get more nutrients. The components mostly changed for the adaptations to eat the new African environment are the shape, size, and thickness of teeth, jaw muscles, jaw bones, the maxilla and mandible.

Teeth mand25c325adbulas

There was big push for big grinding posterior teeth for there type of chewing that could withstand the endlessly repetition of powerful chewing and be able to bite forcible with out damaging the teeth. The forceful chewing also created thick molar enamel that could withstand the chewing. There was also a trade off for smaller canines as they weren’t being used as usefully as their ape counter part who used them for peeling tough fruit. You can see this progressive trade off from earlier australopiths who had bigger canines then the later specious of the genus. Apes also have thinner molar enamel and higher cusps in there molars for sheering there food unlike australopiths who grinded their food with thick enamel and flat molars.

Jaw Muscles

robustvshomo2

They needed large jaw muscles to be able to chew so forcefully on their food. The robust australopiths are the extremists in this category for they had such large temporalis muscles they had a boney crest called a sagital crest for more muscle. They also had widely expanded zygomatic arches that some robust austslopiths faces were as wide as it was long. The expansion was for more room for the masseter chewing muscles.

Jaw bones

tumblr_mg9rfushlq1r46foao1_1280

There jaw bones, maxillas, and mandible, were also under selective strain to be tougher so that they didn’t fracture under strain which would be game over if you could noteat. So their jaws  developed to be thicker, taller, and wider to lower the stress of chewing forcible to obtain the nutrients in there diet.

icoy36063012-donald-johanson161028170511-1477667246520
Donald Johanson. The Discoverer of Australopithecus afarensis (Lucy)

 

 

Legacy:

Gracile australopiths would eventually lead to the genus Homo and the robust became extinct probably because their more specialized adaptations lead to a less flexible diet as climate change continued in Africa. Even today we still have a reflection of what the australopiths left as we became there decedents. Like a more diverse diet less dependent on fruit, adaptations that was continued as we developed into our more specialized bipedal moment, grinding chewing as we chew with thick molar enamel, and small incisor-like canines.

For more information

The Story of the Human Body by Daniel Lieberman

http://kcur.org/post/dental-detectives-what-fossil-teeth-reveal-about-ancestral-human-diets#stream/0

step01-600x495

 

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.

2011-06-30-anthropology

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.

220px-franzboas
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.

margaret-mead-3
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.

louis-and-mary
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.