Wednesday, June 01, 2011

Making An Army on Horseback Out of A Nail That Might be From a Horse-Shoe. Today's Science Critique.

Lots of research into the possible ancestors of modern humans does that. There is a find of something, but nobody can actually tell whether what was found represents a common aspect of the life of the studied hominids. The find consists of not much: A few bones or some remains of a possible camp-site or some fossilized footprints. Then one builds theories on that basis.

I'm not saying that the theories are necessarily wrong ones but we really have very little actual evidence, and most of that could lend itself to several different interpretations. Too often the suggested interpretations become what we learn from the research, not what it really, truly found.

Then the interpretations get further interpreted by our current popular culture. Or by earlier cultures; we still get cartoons about the "caveman" going out hunting while the "cave-housewife" stayed behind to mind the children in the "cave-nuclear-family."

A recent piece demonstrates all this. Note that it is not a bad piece of research, not at all. It is just limited by the problems I discussed:

That we really don't know how representative the few finds we have are, that most of the finds don't tell us much about the sociological frame for the find and that the numbers of finds are exceedingly few. In some ways it is as if an archeologist finds a nail which could have come from a horse-shoe and then slowly moves into the argument that an army with horses and riders must have traveled through the area.

Here is the study which started all these thoughts:
Ancient forerunners of modern men stayed close to where they were born but paired up with females from far beyond their local stomping grounds, a new study claims.
The research provides a rare insight into the social behaviour of primitive "hominins" that appears to match closely that seen in chimpanzees and bonobos today.
Scientists analysed fossilised remains around cave networks near Johannesburg in South Africa and found that while 90% of males appeared to have spent their whole lives in the area, at least half the females had come from farther afield.
The work suggests that males regularly stayed with the community they were born into, with females roaming into new territories as they reached sexual maturity, the scientists report in the journal, Nature.
This is the it-must-have-been-a-horse stage. The earlier stage, that of finding the nail from the horse-shoe, involved looking at the fossilized teeth of two extinct species to analyze the amount of strontium in them. Strontium levels may be linked to the area in which the individual grew up. The research found that:
The strontium tests revealed that most of the individuals lived and died in the same area, where the rock is dominated by a limestone called dolomite. But results from the smaller teeth, which most likely came from females, showed many must have spent their youth elsewhere.
This doesn't sound bad at all, right? But when you find that the percentages (90% of males, at least half of females) in the first quote above were based on EIGHT Australopithecus africanus individuals and ELEVEN Paranthropus robustus individuals you might begin to see the horse-shoe aspect of the problem. Only the Australopithecus africanus is regarded as a possible forerunner of modern humans, by the way. Thus, from one nail to a horse-shoe.

But the results are then interpreted to get that army on horseback:
"Here we have the first direct glimpse of the geographic movements of early hominids, and it appears the females preferentially moved away from their residential groups," said lead author, Sandi Copeland at the Max Planck Institute for Evolutionary Anthropology in Leipzig.
A similar situation is seen among modern chimpanzees, where females tend to move out of their groups, in part because males form strong ties that help them protect a troop's territory.
"By virtue of the fact that the males choose to remain, the females are indirectly forced to leave their communities in order to avoid close inbreeding. It could be that among these early hominins, female dispersal has some correlation to close cooperative behaviour between males," Copeland added.
Perhaps. Or the small teeth might not be female teeth at all. Or the females might have been kidnapped by the males from other groups. Or, as the title of the quoted piece suggests, perhaps females were the ones with the wanderlust? And where all these finds from roughly the same time period? From the same groups? Could it be that the teeth belong to different times and different groups?

Neither do we know anything about the cooperative behavior of the hominid males, or even whether the males "chose" to remain in the same communities.

The final round in the horse-shoe games always consists of the popularizations. The Guardian isn't really playing that game, even inserting a different interpretation by the choice of the headline. But think how the story would be interpreted if the findings had been that it was the male hominids who appear to have come from elsewhere.

The interpretation would not be about female cooperation as the reason for their dispersal. It would be all about man-the-explorer, and how that aspect of men explains their current dominance in various ways.