Was the LCA in Europe????

Was the last common ancestor of apes and humans in Europe?  That seems to be the gist of a study published in the PLoS One.  Nicole Mortillaro, of CBC News reports:

A jawbone discovered by German troops in Athens during the Second World War could be evidence that apes and humans diverged 200,000 years earlier than the current theory says.

Chimpanzees and bonobos are the nearest known relatives to humans, sharing 99 per cent of our DNA. It's believed that we split between five and seven million years ago.

However, researchers analyzing two fossils — a jawbone from a German museum and an upper premolar from a collection in Bulgaria — concluded their ages to be roughly 7.2 million years, and belonging to a pre-human.

From the paper in PLoS:

The split of our own clade from the Panini is undocumented in the fossil record. To fill this gap we investigated the dentognathic morphology of Graecopithecus freybergi from Pyrgos Vassilissis (Greece) and cf. Graecopithecus sp. from Azmaka (Bulgaria), using new μCT and 3D reconstructions of the two known specimens. Pyrgos Vassilissis and Azmaka are currently dated to the early Messinian at 7.175 Ma and 7.24 Ma. Mainly based on its external preservation and the previously vague dating, Graecopithecus is often referred to as nomen dubium. The examination of its previously unknown dental root and pulp canal morphology confirms the taxonomic distinction from the significantly older northern Greek hominine Ouranopithecus. Furthermore, it shows features that point to a possible phylogenetic affinity with hominins. G. freybergi uniquely shares p4 partial root fusion and a possible canine root reduction with this tribe and therefore, provides intriguing evidence of what could be the oldest known hominin.

Hominin, in this case, means humans and their premodern forms.  I think it is more than somewhat suspect to base a far-reaching hypothesis on one trait, even if it is the p⁴ root. It is commonly held that the last common ancestor of apes and humans was in Africa, sometime around 7.5 to 8 million years ago, but we have no fossil evidence to support that position.  While it is certainly true that the further back in time you go, the more ape-like our ancestors get, there is simply no smoking gun.

The world will not end if the LCA is, in fact, in southern Europe, but if it is, then it raises some interesting questions.  For one, if the LCA is in Europe, why are all of its hominin descendants in Africa?  So far, even discounting Sahelanthropus, which is a surface find and was crushed, all of the late Miocene and early Pliocene hominin remains are found in either the Afar triangle (Ardipithecus) or the Tugen Hills, in Kenya (Orrorin tugenensis).  If you add Sahelanthropus, then Chad comes into the picture. Additionally, why have we found no post-split hominids in southern Europe?  So far, all that has come out of the ground in this region is middle to late Miocene apes.

Other hurdles exist to acceptance of this idea.  For one, it is pretty clear that our closest living relatives, genetically, are the chimpanzees, who reside in the tropics of central Africa.   Next on the list is the gorilla, also found in the tropics of Africa.  Why have we found no precursors to these hominoids in southern Europe? 

On the other hand, the fossil find has been securely dated to the Messinian Event, in which the Mediterranean Sea effectively dried up, suggesting the possibility that the ancestors of the Pliocene hominins from North Africa migrated from southern Greece.  If this is so, then it raises the dark and ominous thought that much of the information regarding the LCA lies at the bottom of the Mediterranean Sea. That is terrible to contemplate.  This would also mean that Chimpanzees and Gorillas are the survivors of a group of Miocene apes that ranged from southern Europe to central Africa.  We know that the ancestors of chimpanzees once upon a time occupied the East African Rift Valley, but are now restricted to central and west Africa.   If their original range extended up into Egypt and beyond, then perhaps we are looking at a similar situation for their ancestors, as well.  

A whole lot more investigation needs to be done and more fossil remains need to be found to shore up the European LCA hypothesis.  Given that this new information does not come from newly discovered fossils does not raise my hopes. 

A Good Video on Radiometric Dating

Joy Walters has a video on BioLogos that explains in layman's terms why radiometric dating is sound and how hominin/hominid fossils have been dated. Go watch!

Geologically Recent Ape in Europe

Deutsche Welle world has an interesting story about dental remains that have been discovered in Europe that put Miocene apes in the region as recently as 7 million years ago. According to the story:

"The latest data have shown that contrary to the hominids in Western and Central Europe (with the exception of the insular Oreopithecus), hominids from the Eastern Mediterranean may have lived up to 8 to 7.5 [million years ago], preadapted to the more open biotopes of the Balkan-Iranian zoographic province," the team wrote.

What is important to note about this story (and it threw me for a minute) is that the author is using the newer phylogenetic systematics-driven definition of “hominid.” In this scheme, “hominids” are now at the family level and include us and all of the great apes and “hominins” (us and our ancestors) are at the sub-family level.

A problem, voiced by one of the excavators, is, of course, that it is just one tooth, so we cannot say too much about it. Still, it is interesting if it bears up.

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Gibbons and Siamangs Booted off the Island

Science Daily has a story about a new Primate phylogenetic tree that has been derived from sequencing 54 genetic regions in 186 species. Over the course of the last twenty years or so, with the advent of the genetic revolution, there has been a wave of new information about the higher apes that has allowed us to break them out of their “grade” of higher apes and place them more accurately taxonomically.


It now appears that gibbons and siamangs (Hylobates, Nomascus and Symphalangus) are monophyletic with respect to the clade that includes gorillas, chimpanzees, orangs and us. I have reproduced the relevant part of the image in the PLoS article to the left. About them, the authors of the article write:

The eight species included in this study form three clades that coincide with genus designation (absent is Hoolock; nodes 64–69) that diverged rapidly 8.9 MYA. Moreover, Nomascus species appear more recent than Symphalangus and Hylobates, with node divergence dates estimated at less than 1 MY (Table 3, Table S9, Figure 2). Thus, Hylobatidae exhibits episodes of rapid divergence perhaps related to excessive genome re-organization and warrants additional investigation.

Another piece of the puzzle.

Hat Tip to Bill Myers.

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And Lo, It Was Hot...

ScienceDaily is reporting on some research in the Turkana Basin, the area where many early hominid fossils have been found, has been a scorching place for at least 3 million years. They write:

Their findings -- which were based on measurements of the spatial distribution and concentrations of isotopes in carbonate ions -- are being reported this week in the early online edition of the Proceedings of the National Academy of Sciences (PNAS). "When you measure the temperature of the ground, you learn a lot about the environment above it," says John Eiler, Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech. In fact, he says, soil temperature tells you not just about air temperature, but about whether there were trees and plants to shade the soil, keeping temperatures cooler during the hottest part of the day.

It is suggested that these kinds of conditions, in which the forests retreated led to the earliest hominids trying to minimize their heat exposure. This would have been done two ways: sweating and walking upright.

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Itadakimasu!

That's Japanese for "Let's eat!" Taragana is reporting on research done on early hominids to determine what they ate. The answer:

Our early ancestors, living in what is now northern Kenya, feasted on fish and other aquatic animals such as turtles and crocodiles - foods which probably played a major role in the development of a larger, more human-like brain, new research reveals.

The study, which offers the first-ever evidence of dietary variety among early pre-humans, appears in Proceedings of the National Academy of Sciences. A team of researchers that included Johns Hopkins University geologist has found that early hominids living in what is now northern Kenya ate a wider variety of foods than previously thought, including fish and aquatic animals such as turtles and crocodiles. Rich in protein and nutrients, these foods may have played a key role in the development of a larger, more human-like brain in our early forebears, which some anthropologists believe happened around 2 million years ago, according to the researchers’ study.

It takes quite a bit of intelligence to incorporate all of those different kinds of foods into a single diet. It is always interesting to see a report like this that basically ends "they were smarter than we thought."

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Not Out of the Trees?

The Independent has a story about research indicating that our earliest human precursors might not have been as arboreal as originally thought. Michael McCarthy writes:

Humanity's immediate predecessors may have had trouble climbing trees, research suggests – so they may not have been as ape
-like as many experts believe.

Scientists have arrived at this conclusion after making a close study of the way chimpanzees scale trees – virtually vertically and with ease – and then comparing chimpanzee ankle joints with those of hominins, humans' ancestors.

The hominins lived between 1.5 and 4.1 million years ago, a relatively short time after proto-humans and chimpanzees split from a common ancestor (generally thought to have been between four and eight million years ago). Many experts have argued that this ancestor was probably quite chimpanzee-like, and as a result it has been widely assumed that the earliest humans were ape-like, too.

Given what we know about the bipedalism of Ardipithecus and Australopithecus afarensis, this doesn't seem to me to be too much of a surprise. It is quite possible that bipedality evolved due to selective pressures for a more terrestrial lifestyle, perhaps because they were being out competed by the precursors of modern chimpanzees.

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More on the Hominid Discovery

The Telegraph has a larger, more in-depth article on the discovery in South Africa of the early Homo remains. Richard Gray writes:

Experts who have seen the skeleton say it shares characteristics with Homo habilis, whose emergence 2.5 million years ago is seen as a key stage in the evolution of our species.

The new discovery could help to rewrite the history of human evolution by filling in crucial gaps in the scientific knowledge.

Most fossilised hominid remains are little more than scattered fragments of bone, so the discovery of an almost-complete skeleton will allow scientists to answer key questions about what our early ancestors looked like and when they began walking upright on two legs.

This discovery was hinted at months ago but no details had been forthcoming. One of the problems that continually plagues palaeoanthropology research is sections for which the fossil record is not as good as we would like it. There are a number of Homo habilis fossils that show a clear evolution of Homo but only a few instances in which it appears as though there is a clear transition between australopithecines and Homo habilis. This may change that.

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Possible New Hominid Species Discovered in Siberia

Reuters is running with a story about genetic research being done on hominid material discovered in Siberia that, according to researchers, suggests the presence of a new species of hominid that lived until around 30 thousand years ago. The author writes:

"It really just looked like something we had never seen before," Johannes Krause of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told a telephone briefing.

"It was a sequence that looked something like humans but really quite different."

Writing in Nature, Krause and colleagues said they sequenced DNA from the mitochondria, a part of the cell, which is passed down virtually intact from a woman to her children. They compared it to DNA from humans, Neanderthals and apes.

The sequence indicates the hominin's line diverged about a million years ago from the line that gave rise to both humans and Neanderthals and that split about 500,000 years ago.

I always have grave misgivings when geneticists, in the complete absence of diagnostic palaeontological material, proclaim that a new species has been discovered. For one thing, we don't have the genetic sequences for the intermediates between the find in Siberia and contemporary humans. How many substitutions denote a different species? This is where systematics can get away from us. If we don't have the intermediates, how do we know where the proper branch is? To be fair, the researchers, themselves, are reticent to go the 'new species' route yet but it seems they are leaning that way.

Smithsonian: Discovering Our Ancestors

The March issue of The Smithsonian Magazine has a large spread on the recent advances in human origins, including a large article on the discovery and identification of Ardipithecus ramidus by Ann Gibbons. One of the striking things about the find is the locale in which it took place: literally a palaeoanthropologist's dream come true. Gibbons writes:

As we wait for the Alisera to arrive, White explains that the team returns to this hostile spot year after year because it’s the only place in the world to yield fossils that span such a long stretch of human evolution, some six million years. In addition to Ardi, a possible direct ancestor, it is possible here to find hominid fossils from as recently as 160,000 years ago—an early Homo sapiens like us—all the way back to Ardipithecus kadabba, one of the earliest known hominids, who lived almost six million years ago. At last count, the Middle Awash project, which takes its name from this patch of the Afar desert and includes 70 scientists from 18 nations, has found 300 specimens from seven different hominid species that lived here one after the other.

It is the palaeoanthropological equivalent of the Liaoning shale fossil beds in China that have yielded so many dinosaur remains. Her description of what the remains of Ardipithecus represent is evocative:

One thing that is clear is that these early fossils belong in a class by themselves. These species did not look or act like other known apes or like Lucy and other members of Australopithecus. They were large-bodied ground dwellers that stood up and walked on two legs. But if you watched them move, you would not mistake them for Lucy’s species. They clung to life in the trees, but were poised to venture into more open country.

Becoming human, one slow step at a time. It is a pity that we do not have any more remains of Ardipithecus kadabba, which preceded A. ramidus by around a million years. What kind of individual would that be? Would he or she walk upright? Would we see any incipient hominid characteristics? At this point, quite literally, only God knows.
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Cold Weather and Bigger Brains

Bob Holmes of the NewScientist has a report on brain size and hominid evolution, in which it is hypothesized that modern human brains could only expand when the air temperature was cold enough to allow for adequate heat dissipation—a glacial maximum for example. He writes:

For all its advantages, the modern human brain is a huge energy glutton, accounting for nearly half of our resting metabolic rate. About a decade ago, biologists David Schwartzman and George Middendorf of Howard University in Washington DC hypothesised that our modern brain could not have evolved until the Quaternary ice age started, about 2.5 million years ago. They reckoned such a large brain would have generated heat faster than it could dissipate it in the warmer climate of earlier times, but they lacked evidence to back their hypothesis.

Now hints of that evidence are beginning to emerge. Climate researcher Axel Kleidon of the Max Planck Institute for Biogeochemistry in Jena, Germany, modelled present-day temperature, humidity and wind conditions around the world using an Earth-systems computer model. He used these factors to predict the maximum rate at which a modern human brain can lose heat in different regions. He found that, even today, the ability to dissipate heat should restrict the activity of people in many tropical regions (Climatic Change, vol 95, p 405).

One of the big questions surrounding the research is whether or not the climate data has the kind of resolution that is necessary to support the hypothesis:

Given the timescales involved, it may be near-impossible to match definitively the onset of an ice age with speciation, but a 1.5 °C drop is consistent with the cooling climate of the time, says Middendorf.

It is an intriguing idea and bears more investigation but I suspect it may be one of many variables driving brain size expansion at the time.


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Dating Hominids Based on What the Animals at the Sites Ate

ScienceDaily has a story on how to date fossil hominid sites based on the dental remains of the animals that lived around them. As the story relates:

Florent Rivals is the main author and a researcher from the Catalan Institute for Research and Advanced Studies (ICREA), attached to the IPHES in Tarragona. "For the first time, a method has been put forward which allows us to establish the relative length of the human occupations at archaeological sites as, up until now, it was difficult to ascertain the difference between, for example, a single long-term occupation and a succession of shorter seasonal occupations in the same place", he explained to SINC.

In the study, recently published in the Journal of Human Evolution, the researchers analyze the dental wear of the ungulates (herbivorous mammals) caused by microscopic particles of opaline silica in plants. These marks appear when eating takes place and erase the previous ones. This is why they are so useful.

This almost qualifies as a taphonomic technique and to have it as an extra tool in trying to figure out how these people lived and what they ate is good news.



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After All, If You Can't Laugh at Yourself...

The June 4 issue of Current Biology contains a study indicating that laughter goes back beyond the ape-human split. The article, in Thaindian reports:

“This study is the first phylogenetic test of the evolutionary continuity of a human emotional expression,” said Marina Davila Ross of the University of Portsmouth in the United Kingdom.

“It supports the idea that there is laughter in apes,” she added.

To reach the conclusion, researchers analysed the recorded sounds of tickle-induced vocalizations produced by infant and juvenile orangutans, chimpanzees, gorillas, and bonobos, as well as those of human infants. A quantitative phylogenetic analysis of those acoustic data found that the best “tree” to represent the evolutionary relationships among those sounds matched the known evolutionary relationships among the five species based on genetics.

The researchers said that the findings support a common evolutionary origin for the human and ape tickle-induced expressions.They also show that laughter evolved gradually over the last 10 to 16 million years of primate evolutionary history.

But human laughter is nonetheless acoustically distinct from that of great apes and reached that state through an evident exaggeration of pre-existing acoustic features after the hominin separation from ancestors shared with bonobos and chimps, about 4.5 to 6 million years ago, Davila Ross says.

Uh, not 4.5 to 6 mya. Not if Orrorin and Sahelanthropus represent incipient hominids. More like 9 to 10 mya. Still, it is nice to know we share such a stress-reducing behavior.