Anthropology.net

I just love saying, “Another Homo in the family”! Anyways, it seems like a new species of Homo has been identified from a partial skull found in Sterkfontein Caves, near Johannesburg by anthropologist Dr. Darren Curnoe from University of New South Wales (School of Biological, Earth and Environmental Sciences) and paleoanthropologist Dr. Phillip Tobias. This specimen, known only by its museum catalog name Stw 53, was  found in 1977 and had largely been ignored until Dr. Curnoe restored and reconstructed the skull with Dr. Tobias. They had initially concluded that Stw 53 is a Homo habilis but after years of examination and comparing it with other fossils, they are both confident that Stw 53 is a new species and named it Homo gautengensis.

Side by side comparison. Stw 53 (Homo gautengensis), (left) and KNM ER 1813 (Homo habilis), (right). H. gautengensis photo by Dr. Darren Curnoe and H. habilis photo from Wikipedia.

Dr. Curnoe believe that H. gautengensis predates H. habilis, making it the earliest Homo in our family tree so far. H. gautengensis walked upright in southern Africa about two million years ago until 600,000 years ago. Fully grown, it stood about 3 feet tall (just over 1 meter tall) and weigh about 110 lbs (about 50 kilograms). It has relatively large molars and premolars, which suggest that its diet consist large of plant matter and requires a lot of chewing. There were stone tools found near Stw 53, described as “fairly primitive” by Dr. Curnoe. They are also thought to have the knowledge of fire, perhaps using it to obtain and/or prepare food. Stw 53 was found in the same caves with Australopithecus africanus and Australopithecus robustus (or Paranthropus robustus). However, Dr. Curnoe does not believe that H. gautengensis gave rise to Homo sapiens.

Reference:

Beale B. 2010. New species of human ancestor identified. Retrieved May 21, 2010 http://www.science.unsw.edu.au/news/new-species-of-human/

Originally posted on The Prancing Papio.

Almost every biological anthropology text-book I’ve ever looked at has described the adaptations of human populations to the environments they occupy. Examples they give are the short stalky Inuit adapted to conserving heat in cold environments, the long lanky East African nomads adapted to far distant travels, and the barrel chested Peruvian and Tibetans living in low oxygen environments.

Highland Tibet

Little discussion, beyond correlating ecology and physical observation, is given to these. Actually I lie, the physiology of the barrel chested high altitude occupants is given a couple of sentences as well as an elevated oxygen binding capacity without concentrating their blood.

A paper published in Science several days ago tackles this latter issue. A group of scientists looked for unique alleles among Tibet highlanders and discovered 10 unique oxygen-processing alleles. I don’t have full access to the publication, so can’t tell if these genes encode for completely different functioning proteins or are differentially regulated at high altitudes.

All I can derive is that these genes seem to prevent polycythemia, edematous swelling of the lungs and brain, and hypertension of the pulmonary vasculature, which are all complications of high altitude living.  Two of these genes are EGLN1 and PPARA. PPARA is a peroxisome proliferation proteins that also is a leukotriene antagonist. That is interesting because in obstructive conditions like asthama, leukotrienes induce vasospasm and bronchconstriction. EGLN1 is also has an interesting role,

“it is a protein encoded by this gene catalyzes the post-translational formation of 4-hydroxyproline in hypoxia-inducible factor (HIF) alpha proteins. HIF is a transcriptional complex that plays a central role in mammalian oxygen homeostasis.”

These two genes were significantly associated with the decreased hemoglobin phenotype that is unique to this highland population.

Simonson TS, Yang Y, Huff CD, Yun H, Qin G, Witherspoon DJ, Bai Z, Lorenzo FR, Xing J, Jorde LB, Prchal JT, & Ge R (2010). Genetic Evidence for High-Altitude Adaptation in Tibet. Science (New York, N.Y.) PMID: 20466884

Every time big anthropology news has come out in the last year or so, I’m too busy and drowned under the sea of books and notes for my upcoming exams to immerse myself in it. This happened with Ardipithecus last fall, and now with the draft of the Neandertal genome coming out tomorrow, I can’t help but feel a bit left out. The complete mitochondrial Neandertal genome was released a little under 2 years ago… and now because of high throughput sequencing technology, the draft genome is now complete.

Currently, Science has put up a special section of their website dedicated to this. The news agencies are having issues with embargoes and what not, they put up articles and then take them down. But the word is out, Green and Pääbo’s project to sequence the Neandertal genome is out and there are some interesting findings:

• The comparison of 3 Neandertal samples to 5 modern human genomes showed that Neandertal genome is closer to some populations of modern humans than others
• About 10 loci had distinctly non-African hallmarks
• There’s an attributable 1-4% Neandertal ancestry to non-African modern human populations

There’s a lot more behind this all than I really have time for, unfortunately. So be sure to check out Razib, John Hawks, etc. for all the goodies.

From Nobel Intent comes news of a discovery in the Mendelian genetics of Mirror Movements, a condition that causes people to involuntarily move both sides of their body when they intended to only move one.

Aside from being medically relevant, interesting on a population genetics level, and involved an Iranian family, it also caught my eye because about 3 weeks ago we covered the implications of DCC (deleted in colon cancer gene, I know — very clever!) mutations in my pathology course. DCC mutations are found in the sequence of events that lead up to a special type of familial adenomatous polyposis (FAP), known as Gardner syndromes.  These colon cancers occurs primarily on the left or descending colon. The morphology of FAP cancers lead to a napkin ring like constriction of the colon that present as alternating bouts of diarrhea and constipation. What makes them unique from other FAPs is that they have present with extracolonic manifestation, like bone cancers.

The DCC gene is on the long arm of chromosome 18. I know that it is a cell surface protein responsible for cell-to-cell and cell-to-matrix adhesion. Normally when cells proliferate, they squeeze up on each other and DCC works via contact inhibition to signal a stop in proliferation because conditions are getting too cramped. Therefore, if DCC is deleted, contact inhibition is lost and cell loses ability to proliferate, yielding a dysplastic growth.

Genbank classifies this gene as one that encodes for a netrin 1 receptor, which I did not know before I read this post. I find this really interesting in the relevance of DCC to Mirror Movements. Dr. John Nicholls,of SISSA in Trieste, Italy,  the dude for neurodevelopment, guest lectured my neuroscience course during my second term of medical school last year. I remember him describing netrins as a class of axon guiding proteins that functioned during growth and development. The hallmark experiment I remember him citing was the Oster, et al., 2004, where ganglion cell axon pathfinding in the retina and optic nerve was guided by netrin signals.

It seems that in Mirror Movements, the mutation in DCC prevents it from helping,

“nerve cells on one side of the spinal cord to stay on that side as they extend processes up and down the developing spine…. Because the protein is malformed, the body develops neural connections that route one-sided connections to both sides, producing the mirrored activity.”

I don’t have access to Science unfortunately to research the demographics of the particular SNP they discovered… So I can’t tell you of the gene frequencies… But if anyone does have access to the paper, and doesn’t emailing me, I’ll be very grateful. I love these sorts of discoveries where I learn something new and integrate what I’ve learned the past year and half of medical school!

Srour M, Rivière JB, Pham JM, Dubé MP, Girard S, Morin S, Dion PA, Asselin G, Rochefort D, Hince P, Diab S, Sharafaddinzadeh N, Chouinard S, Théoret H, Charron F, & Rouleau GA (2010). Mutations in DCC cause congenital mirror movements. Science (New York, N.Y.), 328 (5978) PMID: 20431009