Apes like barbecue

A paper in the current Journal of Human Evolution by Victoria Wobber, Brian Hare and Richard Wrangham (Wobber et al.2008) reports on a series of experiments trying to get great apes to eat cooked food. With meat, sweet potatoes and carrots, it seems they like the cooked version better—although with apples and regular potatoes they are indifferent. They also tried to figure out if the apes liked the cooked food because of its taste, texture, or what.

Overall, great apes in these experiments preferred cooked foods to raw, from tubers to meat. However, they did not prefer all foods cooked, being indifferent as to the choice between raw and cooked apple and between raw and cooked white potato. Neophobia could not be eliminated as a contributing factor in some results but, in experiment 4, chimpanzees that were equally unfamiliar with cooked and raw beef still preferred the cooked item. Subjects preferences remained stable across test sessions and across test populations, suggesting that food choices were not strongly shaped by past experience. The different properties being used to select the cooked items were also strongly salient across individuals and populations. This implies something inherently preferable about the effects of cooking which is immediately discernable.

These results support the hypothesis that great apes perceive and prefer properties of cooked food relative to raw, in the case of both starchy foods and meat. It was unclear which properties apes were sensitive to in the cooked food. The results of experiment 2 suggested that subjects may have used texture to discriminate between the carrots of different manipulated consistencies. Yet apes lack of preference for items such as cooked apple, which is softer than raw apple, showed that other factors were involved as well. It is important to note that in both cases where the cooked item was not preferred over the raw (white potato and apple), individuals did not prefer the raw item, but were simply indifferent between the two options. This implies that apes may have chosen the cooked item only when that item seemed signicantly better, with the white potato and apple not showing large enough differ- ences between cooked and raw to create a preference distinction. Future work can investigate which properties of food items altered by cooking are the most salient in determining preferences (Wobber et al.2008, 347)

They put their paper into the context of the evolution of food preference and cooking in hominids. Cooking clearly has some benefits for hominids: it transforms some indigestible foods into useful ones, facilitates energy release from some foods with less digestive requirements, and it reduces the wear and tear on teeth. The question: When did the hominid taste system adapt to match the dietary benefits of cooking? Did hominids start out with a taste for cooked food, which they could satisfy when they invented fire? Or did hominids invent fire for other reasons (e.g., light, protection) and only later adapt their sensory systems to tolerate cooked food?

The study answers this question by showing that the taste preference for some cooked foods may have already been present in ancestral hominids. The fact that all of the great ape species showed a preference for some cooked foods is pretty convincing. It seems that the study included enough trials to show that this wasn’t simply the apes preferring to try something different from their usual diet, although this might bear more checking. One would also want to exclude the possibility that the apes had been smelling cooked foods for many years (as a result of human contact—these being captive apes).

The results raise the question of why exactly apes should exhibit a preference for a style of food they have never eaten, and would never obtain in their natural habitats. We may hypothesize that the same kinds of molecular signals that are present in certain cooked foods are also useful for differentiating between other good and bad foods. This is the explanation favored by Wobber et al.:

Overall, our ndings conform to evidence that wild chimpanzees choose seeds that have been heated by wild res (Brewer, 1978), demonstrating that great apes possess a preference for cooked items. These preferences may be widespread in mammals, as shown by the evidence for rats and cats preferring cooked items (Ramirez, 1992; Bradshaw et al., 2000), and as would be expected from the improved quality of cooked items. Most likely, therefore, early hominids prior to their control of re possessed these preferences as well. This, in turn, suggests that cooking would have spread quickly after it arose, with preferences for the properties of cooked food being exapted from ancestral traits rather than having developed as an adaptation to eating cooked food (Wobber et al.2008, 347).

I find it interesting that the chimpanzees in the study exhibit such a strong preference for cooked meat. Meat gets a lot of attention in both chimpanzee and human groups, and was apparently handled more intensively by early Homo than earlier hominids. I wonder if this might have spurred experimentation to a greater extent than more quotidian plant foods.

<h2 class="likechapterHead"><a   id="x1-2000"></a>References</h2> <a   id="likesection.2"></a><a   id="Q1-1-3"></a>   <div class="thebibliography">   <p class="bibitem" ><span class="biblabel"> <a   id="XWobber:2008"></a><span class="bibsp">&#x00A0;&#x00A0;&#x00A0;</span></span>Wobber V, Hare B, Wrangham R. 2008. Great apes prefer cooked food. J   Hum Evol 55:340&#8211;348. <a  href="http://dx.doi.org/10.1016/j.jhevol.2008.03.003" >doi:10.1016/j.jhevol.2008.03.003</a>. </p>

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