Anthropologist needed: Why make complex tools?

Posted by Jeff Lundy, community karma 227

As a sociologist, I've spent a lot of time studying people -- however, as the old anthropologist's joke goes: "sociology is anthropology done poorly, in our own backyard, covering just a hundred years of history."  In truth, it's only recently that I've started to do some digging into the origins of this species I study all the time.  This leads me to a question:  how on earth did early hominids start using complex tools?

Let me preface this question with what I know already:  1) early hominids like homo habilis made stone tools, including (according to evidence) a simple axe made from a shaped stone attached to a wooden pole.  2) Chimps, along with some monkeys and other apes, use tools.  These include stones for cracking open nuts, and sticks for scooping up ants and termites.

I admit, when I first saw chimps using tools in nature footage, I was floored.  From this footage I learned that there are predilecitons among certian very clever, inquisitive mammals to extend their bodies with simple, one-piece tools.  At first blush this impressed upon me how similar other apes are to ourselves. HOWEVER, now that I've gotten over the surprise, this kind of footage only seems to make human's use of complex tools more astounding.  To make an axe you have to combine three things: stone, wood, and something to bind them.  This is a whole order of magnitude different from the already astounding use of a single-piece tool (like a stick). 

So here's my question again: What pushed homo habilis, who had a brain only 33% bigger than a modern chimp, to do something that no other animal has evidently ever done?  Fundamentally, space ships, skyscrapers, and lasers are amazing, but they are just refinements and adaptations of the facility to make complex tools. 

How the heck did homo habilis get started down this path, what pushed him, and why hasn't any other animal ever been pushed to do the same thing?

almost 12 years ago

1 Comment

Madelynn von Baeyer, community karma 67

This is basically one of the fundamental questions of paleoarchaeology, so forgive me if I my answer contains too many generalizations. There are a few misunderstandings in your question that I think need to be clarified. First of all, Homo habilis did not make complex tools, nor did Homo erectus. The Oldowan and Achulian tool kits that are associated with H. habilis and H. erectus respectively consisted of single nodules shaped into simple hand tools. This is not much more advanced than using a stick as a guide for termites. Tool hafting, attaching a stone point to a handle, does not appear in the archaeological record until Homo neanderthalensis. Evidence for true complex tools, like the bow and arrow, only appears with Homo sapiens. Furthermore, these complex tools first appeared quite early in Africa, before 285 thousand years ago. (Source: McBrearty, S 2007. Down with the revolution. In Mellars, P. & Boyle, K.,eds., Rethinking the Human Revolution. Cambridge, UK: MacDonald Institute, pp. 133-151.)

These technological advances are probably related to increasing brain size, as you mentioned in your question, but the actual change in brain size between chimps and the first makers of compound tools is significantly larger than 33%. The absolute brain size of H. neanderthalensis is 1512 cm3 and for H. sapiens is 1355 cm3, a significant increase from chimpanzees. (Source: Wood, B. & Collard, M. 1999. The human genus. Science 284:65-71.) When taking the brain size data into account, it’s not that hard to understand why other animals have not made the leap to compound and complex tools. I think the combination of primate manual dexterity and large hominin brains created the perfect conditions to develop compound tools.

As for why these tools developed, I think this technology is a cultural adaptation to the environment, as most technology is. H. sapiens and H. neanderthalensis figured out how to haft tools, create microliths, refine knapping to small, delicate points. They experimented with these new techniques and found uses for them. So the answer to your question, I think, is that compound tools are simply another step down a path that was started by a relatively simple task, hand tool knapping, and was transformed by innovation when innovation was possible due to larger, more complex brains. It is important to note that this innovation did not happen quickly either. The Achulian tradition lasted for over 1 million years with little evidence for change. During this time, hominin brains were increasing, but were still not as complex or large as H. neanderthalensis or H. sapiens brains.

almost 12 years ago
Very helpful answer, Madelynn! I had to look up the term "knapping" and thought it might be helpful for other readers to have the definition handy: "Knapping is the shaping of flint, chert, obsidian or other conchoidal fracturing stone through the process of lithic reduction to manufacture stone tools, strikers for flintlock firearms, or to produce flat-faced stones for building or facing walls, and flushwork decoration" (from the Wikipedia page on knapping).
Brian Cody – almost 12 years ago
I've been meaning to reply to this for several days but I've been busy with a houseguest. So: 1) Citations! This is awesome. I can't believe how direct and well-cited your answer is! I guess this is the kind of value you get from a community of academics. 2) By random chance I happened to visit the Smithsonian Natural History museum this weekend and I checked out the section on "Human Origins." Obviously, from your comments and what I saw there, I've learned that the interwebs led me astray -- tool-making is a gradual process spanning 2.6 million years (although, according to the Smithsonian, it picked up more rapidly in the last 1 million?). 3) You've already put me on a great path, and provided some cites for me to check out, but if you have any time for one more question -- can you explain a bit about why human beings have specialized on increasing brain size? I know that birds, mammals, reptiles, and amphibians can share adaptations in common when they live in similar environments (say, webbed feet when they live in water). Some mammals have even adapted wings for flying (kind of like birds), and naked mole rats have the eusocial arrangment found among ants and termites (one breeding queen, different bodies for workers and defenders, etc.). So similar environments have lead to similar evolutionary strategies in terms of bodily form, even among wholly different classes of the animal world. Why is it that only humans seem to have pushed brain size so far? Is it simply an accident of history (say -- other mammals might have, but we went down that path first and as a consequence we've tended to kill others?).
Jeff Lundy – almost 12 years ago
As something of an aside, brain and cognitive scientists are a bit disappointed with the amount of emphasis on brain size. Size really isn't everything... even the concept of the is limited. I think Jeff is on the right track with his answer for why only humans have gotten so smart. It had to happen to some species first, and then once it happened our ancestors were able to dominate their competitors and fill all the niches (so far) in which human-like intelligence is useful. Obviously a lot more can be said about why we evolved our intelligence, some argue sexual-selection for wit, others social coordination, and I'm sure there are other arguments which escape me at the moment.
Michael Bishop – almost 12 years ago
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