Abnormal Interests

An Overview:
The authors start with a review of the problem of Neanderthal extinction and Human ascendancy.

Notwithstanding the appeal of a unified broad theory to explain the demise of Neanderthals, the literature suggests that multiple causes may have done the species in and that no single theory fits all the available data.

They claim that that all or most of the current theorist "can be grouped under the principle of competitive exclusion."

. . . the principle that if two similar species occupy the same niche, only the more efficient survives and the other slowly goes extinct as they compete for resources. Efficiency in this context can have a mechanistic biological basis or a social or behavioral origin. [References omitted]

They then consider the "mechanistic biological basis," which they worry is a "'just so' story" that is not very satisfying. Not satisfying because, first, "It is impossible to determine precisely which biological, physiological, or technological differences might have led to the Neanderthal’s demise" and second, the biological exclusion principle is based on traits of individuals rather than whole populations. As they say,

Humans can create and commit to exchange institutions that promote trade and insurance, and they may organize themselves to reap the gains from trade that emerge from the specialization of labor.

They conclude this opening section with the proper caution that no single theory can completely explain Neanderthal extinction and an introduction of their behavioral model.

The next section is entitled "Evidence of Neanderthal stagnation and early human trade." The heart of their evaluation of Neanderthals is as follows,

Neanderthal technologies did not advance significantly over their long reign, which has been interpreted as evidence of a lack of competition and social interaction, particularly inter-group interactions [References omitted].

I believe that they mean lack of competition among themselves rather than lack of Neanderthal competition with other populations.

On the other hand, concerning early humans they quote, Mithen and Tattersall and Schwartz in support of the view that human communities were well organized, "with division of labor and social stratification"; things missing in the Neanderthal populations. They also point to interaction between early humans in the form of trade "in stone, ivory, and fossil and marine shells." This is against little evidence for trade between the Neanderthals.

They then turn to a detailed discussion of the biological exclusion model. Cranking numbers into a series of modeling equations that depend on the number of "households," the ratios of "skilled" and "unskilled" workers, time, an "arbitrary biological efficiency differential", and other factors they conclude that, depending on the scenario chosen, it took 8828 to 8861 years after humans arrived for Neanderthals to be extinct. This is near the middle of the range of conventional wisdom within the anthropology community. But they see problems. If the Neanderthals were more biologically efficient, they would have survived at the expense of humans.

This brings the authors to their next section. Here they call upon their "behavioral theory of exclusion model." They reintroduce the differences between Neanderthals and humans when it comes to trade and specialization. They investigate three scenarios: A) "skilled hunters hunt, unskilled hunters hunt and produce other good;" B) "complete division of labor, skilled hunters hunt and unskilled hunters produce other goods;" and C) "skilled hunters hunt and produce other goods, unskilled hunters only produce other goods."

The result,

In Scenarios B and C, trade has a non-negative impact on meat consumption for each group, with at least one group consuming more. The net effect is an increase in the growth rate of the human population relative to Neanderthals.

They then crank the numbers using appropriate models with added parameters for the behavioral theory of exclusion. There's a lot of math in all this. They consider two cases: equal biological efficiency and the Neanderthals having the advantage. They correctly assume that if humans had the advantage they would have won anyway. They also consider the effects of differing fertility rates between humans and Neanderthals. In all, seven scenarios are considered. They result in a range of time between 2797 years and 30020 years from the arrival of humans to the extinction of Neanderthals.

The authors conclude that the fate of humans was more precarious than has previously been thought. The dominance of humans came about by economic factors as well as biological factors.

Economic forces have played integral roles in shaping societies throughout recorded human history, and there is no reason to discount either the presence or potential impact of economics in the pre-historic dawning of humanity. Economics might have been the only thing going for us in those early days, even though these forces may have to some extent conflicted with biological forces. We conclude that humans would always prevail if humans and Neanderthals were about equally capable and humans ‘invented’ the appropriate economic institutions. [References omitted]

But then they are thrown back to biological factors. What was it about humans and not Neanderthals that led humans to this invention? Well, it just may have been biological factors.

Three general observations:
Stating with the title, Horan 2005 is decidedly Eurocentric. It is true that Neanderthals remains are only found in Europe and the Middle East, so the discussion of their extinction is properly somewhat Eurocentric. But Homo sapiens were everywhere and their worldwide survival and ascendancy did not necessarily depend on the extinction of the Neanderthal. Perhaps the authors will provide a similar analysis of the ascendancy of Homo sapiens over Homo erectus in Asia and over other Homos in Africa.

Second, despite the frequent reminders that the article was about early humans and Neanderthals, I had to keep forcing myself to remember this non-detail. I could not help but think that any two hypothetical populations analyzed with the same methodologies would yield the same or very similar results.

Third, while I like interdisciplinary studies of this type, it might have been helped if the authors had recruited a paleoanthropologist who specializes in Neanderthals. I don't necessarily mean that such an addition would have changed the results, I think, however, it would have increased the visibility of the paper among anthropologists and perhaps thereby facilitated a broader more interesting scholarly debate. Shogren presented an early draft of Horan 2005 at the 2002-2003 George Town University, Environmental Policy Program and Horan did the same at the summer meetings of the American Agricultural and Economics Association in 2002. I find no record that anthropologists ever publicly vetted it. The authors do thank Jeffery Schwartz and Ian Tattersall, both will known Neanderthal specialists, upon whom they heavily, but not exclusively, rely.

A few amateur questions, some in the form of statements:
If I understood it correctly, the models seem a little too simple: skilled hunted hunted and maybe produced other goods; unskilled hunters hunted or didn't and produced other goods. But I believe that most anthropologists see the mix as a little more complex. The Neanderthal and human diets likely did not consist of hunted animal meat alone. They also likely gathered fruit, roots, and other eatable plants. They also certainly ate insects. They may have been scavengers on occasion. (Perhaps not exactly to the point, they were also likely dietary cannibals on rare occasions.) How would the ideas in Horan 2005 cash out if three divisions of labor were used: skilled hunters, skilled gatherers and those who where not very good at either?

Is the dichotomy between "biological exclusion" and "behavioral exclusion" more than a distinction without a difference at the concept level? While the complexities of human behavior are very far from understood, few would claim that they are not biologically rooted. It is true, as the authors say, biologists focus on individual organisms,

Ever since Darwin, biologists have been prone to consider what is beneficial or costly for the individual organism (i.e., its birth and death rate, or ability to find food and tolerate stress), not the group of individual organisms.

But sometimes the focus is on individual organisms in groups. I think of the biological studies of chimpanzee team hunting, food sharing, or war as examples. Just as the group is made up of individuals, individuals work within the biological constrains and capabilities of the group. Perhaps I missed something here. But "biological exclusion" and "behavioral exclusion" look to me like the two sides of the same coin.

I was bothered a little by the use of the expression "'just so' story" to dismiss biological exclusion. I'm not so sure that the biological exclusion explanation is all that "just so." However, I'm also not sure if my concern is motivated by the facts of a biological explanation in this case or by the current politics of contemporary US biology. Many creationists claim that much of modern biology is a "just so story." I guess I would have liked the authors to say a little more about their claim.

Finally, it is at least possible that direct conflict between humans and Neanderthals contributed to Neanderthal extinction. How would this affect the model? How does the fact that humans had better tools (weapons) contribute to a model?

On the News Release:
It may seem strange in a review of a very technical paper to discuss the press release that announced it. But it is exactly here that many a popular misconception of science and other scholarly work has its origin - the press release. The attempt to make a very detailed and interesting scholarly paper "relevant" or at least to get it popular attention all too often results in the use of phrases like "free trade" or someother modern sounding phrase. In my marketing days, we called these hooks. The result is, the public starts with a false impression of what the scholars are doing. To their credit, none of the authors used the words "free trade" in any quotations that appeared in the release or in the paper itself.

Bottom line:
This is an abnormally interesting article worthy of considerable scholarly debate. I hope anthropologists will join in that debate.