Human Evolution

Nature and Nurture

2011-11-03T15:01:00.000-07:00

BEYOND. Last week, I had the opportunity to read an article from an old issue (sorry for the delay) from The New York Review of Books by Richard Lewontin. The article entitled "It's Even Less in Your Genes" presents a summary and comment on Evelyn Fox Keller's book: "The Mirage of a Space Between Nature and Nurture" (2010). I think that Lewontin's article and Keller's book (is the next one on my list!) bring a fresh air to this "genomic era" (or "post-genomic era"?) where fishing expeditions about "gene-disease association studies" usually oversimplify (or misunderstand?) the role of the environment and what environment means. Let me share one specific paragraph from Lewontin's article: "The attempt to assign the causes of particular diseases and metabolic functions in humans to specific mutations has been a failure, with the exception of few classical cases like sickle-cell anemia. The study of genes for specific diseases has indeed been of limited value. The reason for that limited value is in the very nature of genetics as a way of studying organisms".
Let's think about it....

Anatomically modern humans and Neanderthals: replacement is back...

2011-08-23T17:29:00.000-07:00

TOOLS and GENES. Last July, was published in Science an article where the authors suggest that "....numerical supremacy (modern humans) alone must have been a powerful, if not overwhelming, factor in direct demographic and territorial competition between modern humans and Neandertals". The authors conducted a new statistical analysis of the archaeological evidence around 40,000 ya in European sites. They also mentioned that improved hunting and food processing techniques could have played a role during the replacement. Finally, Mellars and French pointed out that "A range of climatic and associated environmental factors could have played a further, critical role in this demographic replacement and extinction process".
The idea that the neanderthal population size was smaller than we thought once is not new. A genetic study published not too long ago in Science mentioned that "....data suggest that the long-term effective population size of Neandertals was smaller than that of modern humans and extant great apes"
So, replacement is back.....

Anatomically modern humans and Neanderthals interbreeding: more evidence....

2011-07-29T14:52:00.000-07:00

GENES. New genetic evidence recently published in Molecular Biology and Evolution shows that part of the human X chromosome could have a neanderthal origin, suggesting interbreeding between neanderthals and anatomically modern Homo sapiens. After comparing the neanderthal genomic information (released in 2010) with a worldwide sample of X chromosomes sequences from 6092 modern humans, the researchers found that a haplotype present in the neanderthal genome is present in all modern samples except for Sub-Saharan Africa populations. This new finding does not rule out (in my understanding) the Out of Africa model (or Mostly Out of Africa Model), but it's clear that the new genetic data (especially after the release of the neanderthal genome in 2010) is pushing us to review both models (Out of Africa and Multiregional) when trying to explain the origin of modern humans and maybe finally discard the idea of "complete replacement".

News about peopling of the Americas

2011-07-22T14:08:00.000-07:00

GENES, FOSSILS, TOOLS...The last issue of "Evolution: Education and Outreach" (June 2011) is dedicated to the evolutionary theory and its application to New World settlement studies (by the way, I do recommend this journal for those interested in learning and teaching evolution !!). Rolando Gonzalez-Jose is the guest editor of the issue and he is the current president of the Biological Anthropology Association of Argentina (Asociacion de Antropologia Biologica Argentina). Sadly, I do not have too much time to teach this topic (the peopling of the Americas) in my courses (ANTH 202: Introduction to Biological Anthropology; and ANTH 303: Human Origins) but probably, I will reconsider that. I think that this topic is dealing with an interesting debate and can bring a productive discussion into any introductory or advance course about human evolution. It seems that we (or maybe I was the only one?) did not pay too much attention to what happened during the Holocene when teaching introductory courses. Ironic, my research focuses on the Holocene....or human evolutionary immunology (human health) after the agriculture revolution.

Out of Africa or Out from Eurasia?

2011-07-12T09:50:00.000-07:00

TOOLS. New archaeological and geological evidence from Dmanisi (Republic of Georgia) pushed back the fossil occupation of that site around 1.85 mya. As the authors suggest: "These discoveries show that the southern Caucasus was occupied repeatedly before Dmanisi's fossil assemblage accumulated, strengthening the probability that this was part of a core area for the colonization of Eurasia". Moreover (and more provocative) in the final discussion Ferring and colleagues pointed out that: "The case for a possible Eurasian origin of Homo erectus is increasingly supported by chronometric and biogeographic evidence" So, if erectus did not emerged in Africa (as we were suspecting in the last decades), we should continue looking for a more primitive ancestor (Homo habilis or Australopithecus habilis?) that left Africa before the origin of the erectine population. And this opens more discussion (as always).....Which is the ancestral population leading the lineage to modern humans?: a) the habilines from Africa?; b) the erectines from Eurasia?; c) an erectine population that migrated into Africa (from Eurasia)? d).......?
New findings are great and necessary but they add more complexity to our lineage evolution.

Cold-adapted neanderthals: postcranially speaking...

2011-04-29T14:35:00.000-07:00

FOSSILS. Back again. Last February the Journal of Human Evolution published an article where the authors concluded (well, this is the title): "The neanderthal face is not cold adapted". So, I must finally change that part of my neanderthals' lectures in my courses (ANTH 202 and ANTH 303). For the last 3-4 years I was challenging that idea (neanderthal face as an adaptation to cold weather) in my courses after reading different studies about neanderthals way of life, diet and their environments. But previous analyses (large sinuses and craniofacial pneumatization) suggested that the neanderthal face (some traits) evolved as an adaptation to cold environments. Christopher Stringer (one of the authors of the JHE article) wrote in his book about Neanderthals (back in 1993) that "...the Neanderthal nasal form might reflect a unique combination of the effects of low temperatures and humidity on an archaically modeled skull".
So, if the neanderthal face did not evolve as an adaptation to low temperatures.....how do we explain the morphological differences when comparing with anatomically modern humans? The authors of the JHE article do not disagree with the idea that some postcranial traits may reflect adaptation to glacial conditions, but one potential reason for the distinctive neanderthal face is biomechanical..... "...an adaptation to paramasticatory stress, such as the use of the anterior dentition as a vice". The authors do not rule out the potential role of "phenotypic drifting" (and I like that one too).
It is clear that the neanderthal face did not change in the last 20 years but new studies suggest that we must review how do we understand or explain (functionally) their face.

Fattened monkeys as a "proxi" to human obesity?

2011-02-20T14:02:00.000-08:00

BEYOND. In today's edition of The New York Times (cover page) was published an article about using monkeys in different primate research centers to study obesity in humans. The main centers are the Oregon N ational Primate Research Center and the Southwest National Primate Research Center in San Antonio, Texas. Some studies are reporting results on how high fructose corn syrup appears to accelerate the development of obesity and diabetes. While these results sound promising, we should ask if this animal model (closer to us than rats) and the treatment applied (specific diet and intake) is a real "proxi" to human diet / lifestyle and human reaction to that particular experimental conditions. Monkeys (macaques and baboons) are pushed to changed their diets and lifestyles (wild vs. cage) in a short (really short) period of time; while humans are dealing with lifestyle and diet changes since the agriculture revolution (approximately 12,000 ya). In my graduate class (last Fall) about human evolution in health and disease (ANTH 650), and a recent seminar in a colleague's class (ANTH 612) we discussed human obesity taking into consideration the evolutionary perspective, where not only today's diet and lifestyle must be analyzed but past environments and habits must be included in the discussion.
I was happy when reading in the same article (NYT) a colleague's comment where he points out that he "prefers animals that become naturally obese with age, just as many humans do".

Early migration of modern humans into Arabia.....but from where?

2011-02-19T14:01:00.000-08:00

TOOLS. Stone tools (hand axes) were unearthed in the Arabian peninsula in a rock shelter called Jebel Faya. These tools were dated as old as 127,000 years as it was presented in Sc ience last January. The authors suggest that this early expansion of anatomically modern humans took place from Africa and then added that "It is likely that populations expanded and moved through the interior of Arabia, as well as via the coastline, and used adaptive strategies incorporating terrestrial resources" But, other researchers do not share this idea. John Shea of Stony Brook University in New York pointed out that "stone points from Jebel Faya are shorter, thicker and less pointy than those found throughout Africa beginning 100,000 years ago" Moreover, he proposes that the stone tools similarities of Jebel Faya to Indian finds could reflect a different migration, one that came from Asia. Now the debate is open and waiting for more evidence.

Neanderthals did not brush their teeth....

2011-01-17T11:51:00.000-08:00

FOSSILS. In a recent publication from PNAS, a group of researchers found important information from microfossils in dental calculus of neanderthal skeletons from Shanidar Cave (Iraq) and Spy Cave (Belgium). The microfossil analysis showed that neanderthals (in those regions) made use of the diverse plants foods and transformed them into more easily digestible food in part through cooking them. Previous studies in Amud Cave and Kebara Cave also showed that vegetal food was also present in neanderthal diet. Maybe, one of the most interesting aspect of this recent report is the use of fire to cook their food. The authors of this article conclude that "Overall, these data suggest that Neanderthals were capable of complex food-gathering behaviors that included both hunting large game animals and the harvesting and processing of plant foods".
After reviewing another recent article published on PLoS One, where the authors concluded "Results indicate that either Neanderthals and Modern humans did not influence fire regime or that, if they did, their respective influence was comparable at a regional scale, and not as pronounced as that observed in the biomass burning history of Southeast Asia" it seems that not all archaic populations exploited their environment in the same way.

Old modern human from China

2010-11-25T17:54:00.000-08:00

FOSSILS. Last October was published an article in PNAS presenting a new member of our species coming from Zhirendong, China. Ok, one modern human fossil from China? Yes, but 100,000 years old, meaning at least 50,000 years older than the oldest modern that we usually teach in our courses. To be honest, I am still mentioning another old guy from Jinniushan, China that could be older than 200,000y.
Is this new fossil from China (Zhirendong) challenging the Out of Africa model for the origin of modern humans? First the news from the neanderthal genome and now this new fossil from China....Multiregionalists must be really happy because they are having a great year! Or, maybe, Mostly Out of Africa supporters should be the happy ones?

Creative Explosion: European caves or South African Caves?

2010-08-13T08:53:00.000-07:00

TOOLS and BEYOND. Back again and trying to catch up with some news. An article published in the August issue of Scientific American magazine presents a general review from the work conducted in the last two decades by archaeologist Curtis Marean and his team on coastal South African sites. His main findings challenge the previous hypothesis that suggests that earliest modern human behaviors were all found in Europe around 40,000 years ago (and suggesting that this was the departure "place"). The authors wrote that at Pinnacle Point they found evidence that supports the idea that modern humans (at Pinnacle Point) "may be very well the ancestors of everyone in the planet". Marean an colleagues published similar findings in other South African sites such as Blombos Cave suggesting that modern human behaviors emerged earlier that previously accepted. Maybe we must recognize that the "creative explosion" leading to modern human behavior happened at different times in different regions....(by the way, what's the meaning of "modern human behavior?)
If you want to learn more about Pinnacle Point, and the findings presented by Marean and colleagues, you can check a very entertaining link created by Scientific American.

Update: For more information, last September, the Journal of Human Evolution published a special issue on the Pinnacle Point site.

Malaria parasite and human expasion out of Africa

2010-07-27T12:28:00.000-07:00

BEYOND. The July issue of Current Biology presents an article entitled: "Plasmodium falciparum accompanied the human expansion out of Africa" The authors analyzed a data set of 519 P. falciparum isolates from nine populations covering the entire distribution range of the parasite, with populations from sub-Saharan Africa, Southeast Asia, Oceania, and South America. They sequenced two housekeeping genes, P type Ca2+-ATPase and adenylosuccinate lyase, in their entirety for all isolates avoiding any possible bias induced by selection. Their main conclusion is: "....that the genetic diversity of P. falciparum has been primarily shaped by human demography and does not provide evidence for a significant effect of contemporary nationwide malaria interventions based on mass drug administration and/or widespread spraying of DDT". Interestingly, of all populations included in this study, those from Africa are by far the most genetically diverse.....with the exception of Brazil. Why? The authors suggest that the Americas have probably been colonized more recently, possibly through the slave trade.
I have one concern (so far), at the beginning of the Results, the authors formulated their hypothesis: ".....if P. falciparum had been associated with humans for over 50,000 to 60,000 years (the estimated date for the out-of-Africa migration of anatomically modern humans), its current population structure could still carry a signal of human settlement history" but....how accurate is that estimate for the out of Africa migration of anatomically modern humans....?

Lucy and a new friend bring back an old debate

2010-07-16T13:59:00.000-07:00

FOSSILS. Since Lucy's days (Australopithecus afarensis), the debate around the evolution of bipedalism did not stop. Now, a new specimen (3.58 myo from Ethiopia) brought our attention to the old debate. Last week, an article was published in PNAS where the authors conclude "....that bipedality in Australopithecus was highly evolved and that thoracic form differed substantially from that of either extant African ape". Some colleagues agree with that but are more careful when comparing Lucy and Big Man (new fossil) upright walking with our bipedalism and wrote that ".....they were not identical and biomechanically equivalent to people".
New fossils.....still the same old debate.

The first draft of the Neanderthal genome is here (and...is multiregional model re-emerging?)

2010-05-26T07:38:00.000-07:00

GENES. Finally, the first draft of the Neanderthal nuclear genome is here! Well, let me use an analogy that I was using in class when talking with my students about this ambitious project: the "Frankenstein" Neanderthal genome is here. More than 3 billion bases were sequenced from three female bones (3 individuals....that's why "Frankenstein") that were found in Croatia and date back to 38,000 ya. The preliminary and maybe most shocking(?) conclusion is.... when comparing this first Neanderthal nuclear genome draft with 5 living human genomes (from South Africa, West Africa, New Guinea, China, and Europe) Richard Green and colleagues found that the European and both Asians (Asia and Oceania samples) share 1-4% of their genomes, but... both Africans do not. Thus, the first conclusion after this is that Neanderthals interbred with anatomically modern humans (AMH) after modern humans (again, anatomically speaking) left Africa, but before spreading into Europe, Asia and Oceania. Ok, for those that took my courses (Anth 202 or 303) or probably any biological anthropology course, this new evidence suggests that Multiregional model (MRM) is alive (and some colleagues are very happy indeed). But, let's review some other information before making any big conclusions here...
So far, most mitochondrial DNA (mtDNA) studies did not reveal admixture between Neanderthals and AMH (i.e. Currat and Excoffier, 2004; Serre et al, 2004) but we must agree that mtDNA can't solve by itself the interbreeding question. Now the nuclear DNA (nuDNA) is telling a different story, but not what I (we?) was expecting.... I mean, if interbreeding happened between AMH and Neanderthals, it seems that Europe should be the place. But this new study (so far) suggests that it was an earlier encounter that took place probably in Middle East (if not, how can we explain the genetic similarity with modern Asians samples....or , we should think a little further to explain that).
So, is MRM fully re-emerging here? I am not so sure about that, but it seems that the classic Out of Africa (plus replacement) model is under serious problems with this genetic evidence. But, let me bring here one of the final comments from Green et al paper: "Thus, while the Neandertal genome presents a challenge to the simplest version of an 'out of Africa' model for modern human origins, it continues to support the view that the vast majority of genetic variants that exist at appreciable frequencies outside Africa came from Africa with the spread of anatomically modern humans". Perhaps, we are moving into a new Assimilation model (AM). The first AM was proposed by F. Smith and colleagues back in 1989, and re-edited in 2005. Initially, AM sounds like MRM, but is not. As Smith and colleagues wrote five years ago: "AM differs from MRM in that AM recognizes Africa as the likely source of the basic modern human anatomical form and that the modern humans radiating out of Africa have the major, catalytic effect on the emergence moderns in Europe and Asia". Maybe (as many colleagues pointed out) the multiregional scenario for the origin of modern humans should be applied during the late Pleistocene (and not for the last 1 million years or more).
I will strongly recommend my students to read carefully the last segment on Green et al. paper, entitled: "Implications for modern human origins". It is clear that the direction of gene flow, population size (AMH and Neanderthals), population structure and population expansions are key components in this discussion; and not only genes but fossils and tools (too) will continue helping to get closer (only "get closer") to the final answer.
Finally, as everybody is asking, will it be possible to have nuclear genome information from Middle Eastern Neanderthals.... around 80,000 ya? (maybe we are asking too much). Or....it will be more useful to invest money expanding the sample for the modern human genome? (so far only 5 individuals were used in this study).

Besides the entire "interbreeding agenda", a future analysis that is emerging is the search for genes that have evolved (and fixed) recently in our genome (check Table 2 in Green et al, 2010), and this issue deserves a different debate.
Since the Neanderthal genome discussion is just starting, probably this will not be the last post about it....

Australopithecus sediba.....or Homo sediba....or something else?

2010-04-22T09:39:00.000-07:00

A couple of weeks ago was published on Science new fossil material from Malapa, South Africa (1.8-1.9 myo) that could belong to a new species: Australopithecus sediba. But (as you can imagine) not everyone agrees with the taxonomic position of these new fossils. A good summary of all options was presented by John Hawks in his blog, but let me bring here two fragments from the article published by Berger and colleagues to summarize their opinion about these new specimens: a) "Although the skull and skeleton of Au. sediba do evince derived features shared with early Homo, the overall plan is that of a hominin at an australopith adaptive grade", and b) "The Malapa specimens demonstrate that the evolutionary transitions from a small-bodied and perhaps more arboreal-adapted hominin (such as Au. africanus) to a largerbodied, possibly full-striding terrestrial biped (such as H. erectus) occurred in a mosaic fashion". And now I want to think more about the way that we use the following concepts ..... adaptive grade, evolutionary transitions, and mosaic fashion (one of my "favorite" nightmares....).

Homo floresiensis, Homo habilis, and old tools

2010-03-18T09:57:00.000-07:00

The debate around the little man from Flores is back (well, it was always there...). Since 2004, when the study of fossils remains from a hominin from Ling Bua cave, Isla de Flores (Indonesia), was published in Nature, the controversy and debate did not stop. A brief review of the specimens from Ling Bua cave says that this hominin was only about 1 meter in height, fully bipedal, with a small brain size of 417 cc, with human-like teeth, a receding forehead, no chin, and as old as 38,000 to 18,000 years. Who was the Flores hominin? We have (had) different options.......1) a micro-cephalic population, 2) specimens showing a condition associated with deficit of thyroid hormone (cretinism), 3) hominins that had a recessive autosomic condition associated with the growth hormone, 4) the end product of selection for small body size ("island dwarfism"), and 5) a complete different species: Homo floresiensis.
Lats December, a new study around the Flores hominins was published in the Journal of Human Evolution; this cladistic analysis suggests two scenarios: a) H. floresiensis is an early hominin that emerged after Homo rudolfensis (1.86 mya) but before H. habilis (1.66 mya, or after 1.9 mya if the earlier chronology for H. habilis is retained), and b) H. floresiensis branched after H. habilis. And now, in an advance Nature online publication, a new study from the old stone tools found at isla de Flores suggests that hominins had arrived (who?) on Flores by 1 mya. It seems that the team will return to Flores soon, looking for the early Flores hominins and potential ancestors of H. floresiensis.

Australopithecus anamensis = Australopithecus afarensis?

2010-02-19T11:44:00.000-08:00

FOSSILS. I am back (again). One article captured my attention in the last issue of the American Journal of Physical Anthropology: "New hominid fossils from Woranso-Mille (Central Afar, Ethiopia) and taxonomy of early Australopithecus". Haile-Selassie and colleagues suggest that this new fossil evidence from Woranso-Mille site in Ethiopia will help us to fill the gap between 3.6 and 3.9 mya; and at the end they are questioning that after these new specimens the morphological differences between A. anamensis and A. afarensis do not warrant a species level distinction. Let me bring one of the last comments in their Discussion: " ..... the Woranso-Mille hominids are temporally and morphologically intermediate between the more primitive Au. anamensis from Allia Bay and the slightly derived Au. afarensis sample from Laetoli....... They appear to potentially represent a transitional population within an anagenetically evolving Au. anamensis-Au. afarensis chronospecies"
As always, the species concept in paleoanthropology is bringing another debate...

A new visit to FOXP2 and language

2009-11-13T09:14:00.000-08:00

GENES. News around FOXP2 and human language are back. This time, an interdisciplinary team published a new article about gene transcriptional regulation of the central nervous system by FOXP2. The researchers inserted both versions (alleles) of FOXP2 in human brain cells and looked for transcriptional levels (gene expression) of the genes that FOXp2 regulates. They found that the human version increased the expression of 61 genes and decreased the expression of 51 genes compared with the chimp version of the protein. Moreover, to double-check that the same was happening in real brains, they looked at the expression of these genes in human and chimp brain tissue and found similar expression levels as in the cells.
I like the article, but we must be careful when extrapolating these experimental (in vitro) results, because the development of the human (and chimpanzee) brain is really complex, including a complex concert of different interactions (gene-gene; gene-environment; cell-cell....) that can change the final outcome.
Finally, NatureNews published a comment by Simon Fisher, member of the team that in 2001 reported the link between FOXP2 and language, he pointed out that it seems that language did not evolve from scratch but depended on the retuning of genetic pathways present in non-verbal ancestors, rather than the appearance of completely novel mechanisms. I found this interpretation really interesting and leading (in my understanding) to an important evolutionary concept: exaptation!!
Now the authors wants more, and they will investigate these 61 genes looking for their specific site of expression and their functional role in brain cells; that's great, so let's wait for more news in a near future....

"Ida" in May, "Ardi" in October....

2009-10-01T19:58:00.000-07:00

Now is time for "Ardi". This new finding did not generate a new genus or species in the hominin family, but is giving a lot of information to expand our knowledge about this early hominin group. During a meeting of the American Association of Physical Anthropologists, a publisher told me that his company was keeping "on hold" a new textbook because Tim White and colleagues were close to publish a new shocking fossil. The publisher had the correct information. "Ardi" is coming with a lot of attention from the press, as "Ida" did it not too long ago; but if we want to talk about human evolution, I think that "Ardi" deserves more attention. This new specimen belongs to a genus and species presented during the last decade of last century: Ardipithecus ramidus. The remains correspond to an adult female (4.4 myo), and it seems that she was not alone in Middle Awash (Ethiopia), because the team found dental remains from more than 30 individuals!! Today, Science journal presented "Ardi" on the cover and with 11 articles (47 authors) trying to describe her biology and behavior. A clear summary was presented in the same issue by science correspondent Ann Gibbons. It seems (so far) that "Ardi" was a facultative biped (biped on the ground and moving on all four legs on the trees). Maybe, this is not new for some early hominins, but the grasping foot anatomy calls for some attention. Ok, some colleagues say....is like an ape foot, but other anatomical features are not. Tim White (co-director of the Middle Awash team) pointed out in a very informative video that "Ardi" is another snapshot in our evolutionary history....but he says that this is one of the best and more complete snapshots.
This is the beginning for "Ardi" (and her relatives); a new shocking fossil that will have more than one cover in coming textbooks....

"Ida" fossil and the missing link paradigm

2009-09-25T13:52:00.000-07:00

FOSSILS. I am back, and I want to resume the blog with a brief comment about "Ida" (Darwinius masillae). During last Summer I got emails from some students asking about Ida, and if it was possible that a primate from the Eocene could be considered "The" missing link. The article a bou t Ida was published last May, and after that a huge cataract of information (and maybe misinformation) was shown in the news and TV; the Google icon received Ida's visit during that week of May! Moreover, now we have available a very well done website about Ida. It is clear that Ida represents an important and very complete fossil, and it will give us a lot of information about the Eocene primates. This amazing fossil belongs somewhere closer to the "base" of the primate tree, meaning that does not necessarily make Ida a "close relative" of anthropoids. I will recommend watching a short interview to paleo-anthropologist Tim White on Dolan DNA Learning Center about Ida. In my opinion, White and David Micklos present a clear argument about Ida.
After all, I do not like too much (and maybe I do not understand) the term "missing link"....

Homo erectus medical report: Tuberculosis, bone remodeling, or...?

2009-06-28T10:42:00.000-07:00

FOSSILS. As a researcher interested in human evolution and human immunology I was really excited when Kappelman et al. reported last year the presence of granular impressions in a calvaria of a Homo erectus from Kocavas,Turkey (that has been dated around 500,000 years old) could correspond with a diagnosis of tuberculosis (TB). This observation represented the most ancient example of this disease known for a hominin fossil. However, a recent report by Roberts et al. points out that the lesions observed in this fossil are not characteristic of TB and the diagnosis by Kappelman et al. should be reconsidered. A very interesting argument was also presented by Kappelman et al. in 2008, linking the diagnosis of TB observed in the Kocavas H. erectus and a potential deficiency of vitamin D plus the association with people moving to regions with reduced exposure to ultraviolet radiation..... controversial but provocative!
But it seems that further analysis must be conducted on the Kocavas fossil, and we must wait for a new medical report...

FOXP2 and the evolution language: humans, neanderthals and mice!

2009-06-18T14:12:00.000-07:00

GENES. A colleague from the University of Buenos Aires brought to my attention a recent article from Paabo's team. Using a mouse model they show that the human allele of the FOXP2 gene increases the synaptic plasticity and dendrite connectivity in the brain (basal ganglia). It seems that science is always surprising us, and besides that we must be careful when analyzing results from "exogenus" genes that were introduced in a different species, this new article provides new insights about the evolution of the human language and cognitive capabilities.
What is interesting is that the human allele of the FOXP2 gene (with 2 aminoacid substitutions not found in other non-human primates so far) was found in Neanderthals too.
In this "genomic race" and soon facing the neanderthal genome, I want to bring here one comment from Enard et al. (56 authors!!): "The current challenge, therefore, is not to identify human-specific genomic features, but to distinguish the small number of features that may have phenotypic consequences from the vast majority of functionally neutral features"

Out of Africa? A more complex scenario than we once thought....

2009-05-07T10:54:00.000-07:00

FOSSILS. Last April an article was published on PNAS, and the results challenge the classic Out of Africa model. Gunz and colleagues presented a study of the morphological diversity of the neurocranial anatomy of early anatomically modern humans in relation to that of archaic Homo and modern humans by using methods of geometric morphometrics. Their phenetic analysis confirms doubts raised by genetic studies regarding a "single-dispersal model" proposed by the classic Out of Africa model. Their results are consistent with a model of multiple dispersals events out of Africa. Moreover, the authors suggest that any model consistent with this new analysis requires a more dynamic and a more complex population structure that once thought.
Some colleagues didn't wait too long to make some comments. John Hawks agrees completely with the idea of ancient contributions to the modern gene pool, but he has some issues about how to interpret the morphometric data and their conclusions.

Intersting article, that adds more fuel to the debate....

Old bones, new analysis. What do we do with Homo heidelbergensis?

2009-03-24T14:26:00.000-07:00

FOSSILS. In the last issue (March) of the Journal of Human Evolution an exhaustive analysis was conducted on 36 Pleistocene mandibles from Africa, Asia, and Europe, and 35 extant human mandibles. This study is trying to understand the great diversity in the middle Pleistocene fossil record. The most accepted hypothesis is the one that applies H. heidelbergensis to an Afro-European species that would have preceded the appearance of both classical Neandertals and anatomically modern humans. However, the authors in their final conclusions pointed out that this new analysis does not entirely discount the "European hypothesis" where H. heidelbergensis was ancestral to Neandertals while another African form led to anatomically modern humans.

Ok, I have two (preliminary) conclusions or confusions.....
a) It seems that Homo antecessor is still "alive". But what about the "another African form"?....(Homo rodhesiensis?). And....do we have some "antecessor-like" in Africa....?

b) Or.....basically, we are dealing with a highly polymorphic or variable species in the middle Pleistocene....that's all.

Acheulian handaxes and sexual selection: the debate is back

2009-03-12T09:51:00.001-07:00

TOOLS. Ten years ago, Kohn and Mithen published a provocative article entitled: "Handaxes: products of sexual selection?"(1). In that article they asked: Why were handaxes made and why was their shape symmetrical and regular? They proposed that handaxes functioned not just to butcher animals or process plants but as "Zahavian handicaps", indicating "good genes".
A few weeks ago, the controversy was back again; Nowell and Lee Chang published an article (2), and the title is pretty clear: "The case against sexual selection as an explanation of handaxe morphology". Basically they concluded (after an extensive analysis) that while there is evidence for symmetry preferences in modern humans, there is little evidence that these preferences are the result of sexual selection, and, in fact, most available evidence undermines the putative role of sexual selection in non-human and human primate evolution.

Who is correct?
Maybe we can bring Richard Klein's comment (3) about this issue......."The truth is that hand axes may have been used for every imaginable purpose, and the type probably had more in common with a Swiss Army knife than with a peacock's tail"

(1) Antiquity, 1999, 73, 281: 518-526
(2) PaleoAnthropology, 2009: 77-88
(3) Klein R. and Edgar B., 2002. The Dawn of Human Culture (pg. 107) Wiley and Sons Inc.

1.5 million years old footprints: Whose feet are those?

2009-03-07T13:56:00.000-08:00

FOSSILS. On February 27, Science published new fossil evidence from our ancestors. This time, as in Laetoli (Tanzania), fossil footprints were discovered in East Africa (Kenya). But the new evidence is from a more recent hominin (1.5 myo). Who was walking there ? It seems that (because of the date and place) a Homo species is the best candidate (Homo ergaster /erectus).

But what is interesting is that the authors concluded that "these prints are also morphologically distinct from the 3.75 million year old footprint at Laetoli"; moreover, the authors suggest that these new footprints "show that by 1.5 ma, hominins had evolved an essentially modern human foot function and style of bipedal locomotion"

And we must remember that these footprints are not the only ones that we have (so far) from the Pleistocene; somebody was also walking bipedal in Koobi Fora (Kenya) around that time.....but again, who was (were) there?

So, this new evidence simply re-enforce the idea that while austrolopithecines were bipedal, their bipedalism was not full modern yet (or “full bipedalism" as it is described in the literature).

No elders, no significant culture inheritance: another problem for neandertals?

2009-02-22T12:49:00.000-08:00

FOSSILS. During the first week of February, the Department of Anthropology of The Ohio State University organized a conference entitled: “Evolution Theory, Life History, and Human Longevity”. One of the participants was Rachel Caspari and she presented her work entitled: “Fossil Evidence for Adult Survivorship and Lifespan: Demographic Change and the Evolution of Modern Humans” This talk was summarized by Elizabeth Culotta from Science. After analyzing the teeth of approximately 83 individuals (±120,000 years old) from Kaprina (Croacia), Caspari found that this population died before the age of 30. One of her principal conclusions is associated with the idea that the absence of elders could have had profound consequences for behavior and culture. As Culotta pointed in her comment of Caspari’s lecture: “Older adults can care for and transmit culture to the young…..” leaving the door open for the title of this post.
However, a final Caspari’s remark caught my attention: modern humans from the same time period as Krapina neandertals also seemed to have died young. Moreover, Caspari argued that dying young: "It's not necessarily a species thing"

So, how this could have had significant consequences only for the Kaprina neandertals?
Maybe we must wait for more information (as always….)

Did evolution stop?...or just the opposite?

2009-02-18T19:58:00.000-08:00

BEYOND. Last October I watched an online lecture by Steve Jones that he gave at the University College of London. The title of his conferences was "Is human evolution over?". And (of course) his argument caught immediately the press attention; but also brought strong arguments against his case. John Hawks (University of Wisconsin) did not wait too long to criticize Jones’ argument, and he published a detailed post in his blog. Well, this is not very surprising since Hawks and colleagues published in 2007 a provocative article entitled “Recent acceleration of human adaptive evolution”. And this discussion did not finish yet.
On February 10th, Discover published an interview to Henry Harpending and other colleagues (including John Hawks) entitled: “Human evolution kicks into high gear”. Moreover, at the beginning of this article, the critics also found a new target: the well known evolutionary biologist Stephen Jay Gould. A critic that was also expressed by Gregory Cochran and Henry Harpending is his book “The 10,000 year explosion: how civilization accelerated human evolution”

Here are my (first) open questions:
Who is correct?
What is this all about?
Are they talking about two different evolutionary processes: microevolution (Harpending and colleagues) and macroevolution (Gould, Jones)?

Probably, this will not be my last post about this debate…..

Why this blog?

2009-02-18T11:41:00.001-08:00

As an Assistant Professor in the Department of Anthropology at the University of Louisville, I am teaching different courses about human evolution, human genetics, and human biodiversity. I plan to use this blog as a place where I will post news in the field, that I like to share with my students and with my peers. I hope that some posts will create interesting debates and arguments within the classroom and outside the classroom.
A short comment about the subtitle of this blog ("Genes, Fossils and Beyond..."); while fossils and genes are the most important information when dealing with the study of human evolution, I plan to create a space where other research areas will have representation. I am convinced that the study of human evolution must go "beyond" the traditional fields (within Anthropology and Biology) and should have a significant impact on other areas such as Medicine and Public Health.
One final comment, I am sure that this blog as our own species.....will evolve.
Let's start……