Afarensis is a 3.5-2.8 million year old hominin from the Kada Hadar member of the Hadar formation in the Middle Awash, Ethiopia. He is approximately 41 inches tall, weighs approximately 60 pounds and has a cranial capacity of a whopping 410 cc (approximately). Afarensis is currently considered to be transitional between apes and humans and displays some traits of both. Since he spends a lot of time on the couch watching monster movies, some observers question whether he is an obligate biped (although no one has observed him climbing a tree). He also has a blog called 
Only this time they are in caves. One of the unique aspects of the the Senegal Chimps environment is that it is primarily savanna. According to National Geographic the same population of chimps that use spears to hunt also use caves to avoid the heat during part of the summer:
Even with few direct observations, Pruetz's team was able to assess the extent of cave use using clues left behind on sandy cave floors: tracks, droppings, and food remains.The research showed that cave use was concentrated at the end of the dry season in May and June.
"The behavior appears to be an adjustment to heat stress," Pruetz said.
*snip*
But in Senegal chimpanzees occupy arid savanna habitat dominated by open grassland and sparse woodland. Chimpanzees in these areas exhibit a range of behaviors not found elsewhere.Pruetz noted that cave use is just one of several strategies the chimpanzees use to cope with their difficult environment, where both shade and water are critical resources.
Now you may be thinking that our early ancestors started out on the savanna and you would be correct. Which makes this quote by UC San Diego Jim Moore all the more interesting:
University of California San Diego anthropologist Jim Moore said that while cave use may seem to be an obvious strategy for avoiding the midday sun, the behavior documented by Pruetz's team is unusual."Primates very often don't use available shelter, even to get out of the rain," Moore said.
"The finding opens up a whole set of questions, given that this behavior isn't seen in other regions of Africa," he continued.
"Are they right at the edge of what chimpanzees can handle in terms of temperature ... or is it a cultural thing?"
Long-term studies of forest chimpanzee populations have shown that "historical and fine-scale ecological differences can result in very different cultures [emphasis mine - afarensis]," Moore noted.
Think about the part I bolded for a bit...If these "...historical and fine scale ecological differences..." can result in spear use and cave use by chimps, what kind of effect did they have on the australopithecines (there is some evidence, by the way, the South African species engaged in termite fishing)? Early Homo?
In line with that, I would recommend that you read this guest post by Carl Bajema (editor of Evolution by Sexual Selection Theory: Prior to 1900 over at Evolving Thoughts. Here is the money quote (for our purposes):
The modern version of Darwinian selection theory states that the adaptive evolution is a two step process that occurs every generation--(1) the production of blind genetic variation and (2) the selective multiplication and recombination of genes by the ecologically directed processes of natural and sexual selection. That is, Natural/sexual selection is the set of environmentally directed adaptive processes that are superimposed on the undirected processes that cause genetic mutations. Natural/Sexual selection selectively multiplies adaptive genes and selectively recombines them each generation.
Read the rest of the post, it is fascinating, and think about the chimps in Senegal...
Update 1: Kambiz has some thoughts on the subject as well. He warns us:
...before we say this is a novel-pseudo hominid caveman behavior, let's first remember many other species of animals, such as predatory cats retreat to caves and shade to avoid the heat.
Although slightly guilty of doing precisely that, I have to say I agree with him. For me, the important bit is the "...historical and fine-scale ecological differences can result in very different cultures..." quote. As I point out, this would apply to australopithecines and early Homo as well. I think these types of studies, and the novel and interesting behaviors they bring to light, among chimps can help us to formulate some interesting questions and research strategies to apply to understanding the above mentioned hominins. Especially because the National Geographic article mentions that:
At a place called Baniomba, she said, "[chimpanzees] seem to use caves even more than at Fongoli. But we don't yet have any systematic data."
The research is to be published in journal Primates. I am hoping it will be open access, at any rate this is a story I plan on following...
Comments
Is it odd that Pan troglodytes would go into a cave? Now, if its name were Pan troglobites I would expect to see an unpigmented ape having very long arms and legs and no eyes, perhaps emitting frequent, high-pitched clicking screams.
Posted by: mark | April 10, 2007 9:12 AM
There are several interesting things about savanna-dwelling chimpanzees (and chimps living in seasonally dry environments in general). One is that they exist in that environment; we're often led to believe that this isn't so (we also tend to forget that some gorillas lived in more open areas back when as well, until it became too easy to wipe them out there and populations were only found in the deeper woods). Another is Kortland's findings in the 1960s when he tested wild chimps' reactions to predators with a dummy leopard. A side observation from those tests was that savanna chimps were more accurate throwers and also were more often bipedal during interactions with the dummy than their forest-living kin. Later we found that chimps in such dry areas (not always savanna) dig for water or watery tubers during the dry season. And now we see them making and using tools for hunting.
Very hominid of them.
Posted by: QrazyQat | April 10, 2007 8:03 PM
BTW, I would think that cave use may be esp. helpful for chimps because they don't sweat as effectively as we do. I think it's likely that Moore's "or is it cultural" will be answered by "AND it is cultural" because we have seen for several decades at least that chimps in various areas often find different methods for doing the same thing, and that these methods are then learned (and generally actively taught to young by their mothers) and carried down through generations as a cultural thing (for instance, opening the same kind of nut is done with rocks by some groups, with the teeth by others, and with wood clubs by others; termite and ant fishing is done differently by different groups).
Posted by: QrazyQat | April 10, 2007 8:09 PM
Hey, if the publication comes out in Primates, and you don't have access to it... let me know and I'll do my best to help out.
Kambiz
Posted by: Kambiz Kamrani | April 11, 2007 2:33 PM
Primates is apparently published by Springer. They occasionally have open access stuff, but it looks like I probably will need you to send me a copy when it comes out...
Posted by: afarensis, FCD | April 11, 2007 9:16 PM