Is Homo Floresiensis another Piltdown Man?

2007-02-27T18:51:00.000-05:00

In 2003 as Lord of the Rings dominated at the box office, an article in the journal Nature, revealed a remarkably topical finding: paleontologists had discovered a new diminutive hominid species. The interest in Tolkien's tiny heroes captured the interest of the popular media. Homo floresiensis, - affectionately known as a Hobbit - was the newest addition to the hominid family tree.

However the more interesting aspects of this story occurred following the article's release. Shortly after the announcement of a new hominid species, experts were quick to decry its credibility.

A controversy loomed; and who doesn't love a good controversy? Was Homo floresiensis really a new species or a misidentified Homo erectus fossil? Still others suggested the fossil was nothing more than a Homo sapien with secondary microcephaly. What could this mean for evolutionary theory?

Common Language:

Simply stated: ancestral fossils of any hominid are found infrequently, and potential evolutionary stopgaps (or species that demonstrate stepping stones from ape to human) are even rarer. The discovery of Homo floresiensis therefore, was another critical piece of the puzzle - at least as far as it's discoverers were concerned.

However, scientists have questioned the validity of the findings. Could the Hobbits be another Piltdown Man? It was suggested that Homo floresiensis was simply a small skeleton of Homo erectus with an brain disorder called microcephaly. [Listen here for more.]

Dean Falk also believes Homo floresiensis may be a new species; and she has substantial evidence to support her claim. Using computer software, she and her team have been able to examine what the brain of Homo floresiensis may have looked like. Her team outlines in a paper in a reputable journal PNAS (Proceedings of the National Academy of Sciences) that the brain of Homo floresiensis was not just small, but extraordinarily complex. Moreover, its complexity revealed a re-wiring that suggested a different structure than human brains!

In investigating this article, I was shocked to find how many hominid species have been discovered in the last 7 years since I took Anthropology. The discoveries have been myriad and substantial and they bring us to our next section.

The Popular Hypotheses:
1) Speculation appears to wage over whether humans actually evolved from the same common ancestor as apes, but I would argue, these speculations are carried out in circles isolated from any real evidence. Homo sapiens most certainly evolved from a shared ancestor with the great apes, and we can demonstrate that in an number of Paleoanthropological ways.
[interested readers may find this page to be an invaluable resource]

2) The questions now are really more about how many steps were involved, which lines produced viable offspring, and when exactly the new species were created. Conveniently for us, the discovery of the Hobbits pits two popular hypotheses on human evolution against each other:

The first, called the "Out of Africa Hypothesis" claims that modern humans are ancestors of a common lineage, that for an unknown reason left Africa and dispersed around the planet.
In contrast, the "Multi-regional Hypothesis" suggests that human ancestors left Africa millions of years ago, and regionally evolved.

The discovery of Homo floresiensis discredits the Multi-regional Hypothesis in an important way: Homo floresiensis was a unique species that could not have evolved into modern humans. In contrast, opponents of the Out of Africa Hypothesis point to hominid fossils as old as 1.8 million years old found in Georgia (former USSR). Thus, the debate rages over which hypothesis could more viably account for our ancestry.

Falk's team's findings appear to support both hypotheses in different ways. Her team suggests that Homo floresiensis may have been alive as recently as 18 000 years ago, simultaneous to Homo sapiens, and may therefore represent an independent but "dead branch" on the hominid family tree. It could be that separate lineages left Africa at different times. Just which ancestors gave rise to Homo sapiens has yet to be instantiated by fossil evidence.

Falk and colleagues' findings suggest that Homo floresiensis may represent an evolutionary branch orthogonal to Homo sapiens in which selection pressures favoured cortical reorganization (i.e., rewiring) and not increases in cortical mass as is thought to be the case with Homo sapiens.

Your Brain Cares If You're Slow

2007-02-27T17:00:00.000-05:00

Well sort of. A report issued last year by some scientists at UCBerkeley (UCSF to be exact)revealed that slow-wave oscillations in brain activity help to organize complex behaviours.

The reporting article makes some fallacious claims, but the larger story is interesting. When the brain transmits information between individual neurons this produces what they call "high-gamma waves" that result in quickly oscillating activity in the brain. In order for these small packets of information to be understood, the researchers claim, the brain recruits and coordinates large areas of the brain show global activity that oscillates in time, but at a slower rate (called theta wave oscillations) with the high-gamma activity.

Common Language:

As I see it, the brain is like a drum set. When you perform a complex activity the brain has to keep time in several different ways, all related to the overall beat. Think of the individual message (high-gamma waves) like a high hat, trilling away at a fast and sometimes infrequent rate. However, those individual messages are always coordinated with the baseline - a slower tempo that keeps the overall structure of the musical beat (here, the theta wave activity). Now, when two separate areas start dancing to the same baseline, suddenly, those two areas communicate better. And not surprisingly, when there is a really strong baseline (theta wave) the high-gamma wave activity matches up with it more; the louder the party, the more everybody dances in sync. Cool, yes?

Those of us who care about the brain should note that the gamma-wave activity appears to be linked to bottom up (perceptual) processes, and is more localized than the theta-wave activity, related to top-down activity (executive control).

I also found this article interesting because it reminded me of a concept I recently stumbled across called emergence. Hopefully, I'll be able to do a more complete entry on emergence soon, but the gist of it is this: when studying complex systems, sometimes the behaviour of the whole is more meaningful than the individual parts.

The Popular Hypothesis:
The brain organizes neural activity not only spatially, but temporally; and importantly, multiple rhythmical oscillations in cortical activity may allow the brain to process information -- related to a task -- in the same cortical areas, but for different task functions.

Popular Hypothesis Details

Is Homo Floresiensis another Piltdown Man?

Your Brain Cares If You're Slow