Patterns in the Fossil Record

Science Daily has a post on research about patterns in the fossil record that comes out of the Santa Fe Institute.  They write:

Throughout life's history on earth, biological diversity has gone through ebbs and flows -- periods of rapid evolution and of dramatic extinctions. We know this, at least in part, through the fossil record of marine invertebrates left behind since the Cambrian period. Remarkably, extreme events of diversification and extinction happen more frequently than a typical, Gaussian, distribution would predict. Instead of the typical bell-shaped curve, the fossil record shows a fat-tailed distribution, with extreme, outlier, events occurring with higher-than-expected probability.

While scientists have long known about this unusual pattern in the fossil record, they have struggled to explain it. 

Now, at last, there is something of an answer.

“Within a lineage of closely related organisms, there should be a conserved evolutionary dynamic. Between different lineages, that dynamic can change,” says [Andy] Rominger. “That is, within clades, related organisms tend to find an effective adaptive strategy and never stray too far. But between these clade-specific fitness peaks are valleys of metaphorically uninhabited space. It turns out, just invoking that simple idea, with some very simple mathematics, described the patterns in the fossil record very well.”

Sometimes, it just pays to rethink something from a different angle. This may open up doors to understanding other patterns in the fossil record.

'Swiss Army knife of prehistoric tools' Found in China

Science Daily is on a roll.  This came out a bit back during the late semester crunch and I didn't get a chance to post about it.  Stone tools have been found in south China that appear to be made using the Levallois technology, which originated during the Middle Stone Age, in Africa.  They write:

A study by an international team of researchers, including from the University of Washington, determines that carved stone tools, also known as Levallois cores, were used in Asia 80,000 to 170,000 years ago. Developed in Africa and Western Europe as far back as 300,000 years ago, the cores are a sign of more-advanced toolmaking -- the "multi-tool" of the prehistoric world -- but, until now, were not believed to have emerged in East Asia until 30,000 to 40,000 years ago.

And now the, somewhat, startling conclusion:

With the find -- and absent human fossils linking the tools to migrating populations -- researchers believe people in Asia developed the technology independently, evidence of similar sets of skills evolving throughout different parts of the ancient world.

This particular conclusion seems somewhat ignorant of the fossil record, which clearly has hominins in the area that have distinct Neandertal traits.  The authors, in fact, even mention the possibility that the appearance of the tools might be tied to these earlier migrations, then seem to dismiss this for reasons that are, in my mind, not clear. 

The site, itself, Guanyindong Cave in Guizhou Province, is not new, having been excavated in the 1960s and 1970s.What is new is the date of 80-170 kya.  Levallois tools were thought to have arrived in the area around 30-40 kya and are seen as the artifacts of a late migration.  This re-dating of the sediments of Guanyindong Cave means that these kinds of tools were in the area some 100 ky earlier than was originally thought.  I do, however, think their evidence for independent origin is sparse. 

New Data on Neandertal Anatomy

Anatomists have reconstructed the rib cage of the Kebara 2 Neandertal to get a better understanding of the trunk of our nearest relatives.  Science Daily has the story:

An international team of scientists has completed the first 3D virtual reconstruction of the ribcage of the most complete Neanderthal skeleton unearthed to date, potentially shedding new light on how this ancient human moved and breathed.

The team, which included researchers from universities in Spain, Israel, and the United States, including the University of Washington, focused on the thorax -- the area of the body containing the rib cage and upper spine, which forms a cavity to house the heart and lungs.

What did they find?

The reconstruction of the thorax, coupled with the team's earlier finding, shows ribs that connect to the spine in an inward direction, forcing the chest cavity outward and allowing the spine to tilt slightly back, with little of the lumbar curve that is part of the modern human skeletal structure. "The differences between a Neanderthal and modern human thorax are striking," said Markus Bastir, senior research scientist at the Laboratory of Virtual Anthropology at the National Museum of Natural History in Spain.

"The Neanderthal spine is located more inside the thorax, which provides more stability," said Gomez-Olivencia. "Also, the thorax is wider in its lower part." This shape of the rib cage suggests a larger diaphragm and thus, greater lung capacity.

In my anthropology class, I teach about the effects of Bergmann's and Allen's rules of body morphology. In the case of Neandertals, the adaptations to the cold were shortened distal limb segments, a large, projecting mid-face and a tendency toward barrel-chestedness. The new study reinforces these ideas.

Interestingly, it should be noted that the Kebara Neandertal is found in Israel, not known for its cold climate.  It is hypothesized that the Neandertal population came down from Eastern Europe to escape the cold (the tundra line was at Vienna).  What is peculiar about the Kebara 2 Neandertal is that it consists only of a body.  Whether he died and his head fell in a stream or some animal carried it off, there is no cranium.  Oddly, what we do have is one of the bones that is preserved least in the fossil record: a hyoid.  It is this that has given us the most information about the Neandertal vocal tract.

Fun stuff.