Until recently, the search for a "founder" human brain has rested on the premise that distinctive human behavior, Only our first vision of early hominid life but some very specific ideas about the antiquity of the human brain itself. That we know anything at all about the earliest human origins is due in large measure to the epic lives and work of Louis and Mary Leakey, whose critically important African discoveries beginning in the 1950s gave us not Very closely at the evolutionary background of this hand, and at the changes that brought it its present anatomic configuration and functional capabilities. It is a daring idea, one which requires us to look Washburn quite specifically insisted that the modern human brain came into being after the hominid, hand became "handier" with tools, maintaining that the brain was the last organ to evolve. Theīrain itself, and then society, ultimately overwhelmed the jungle (metaphorically speaking) as a destabilizing element and an organizing force in this process, with increasingly powerful effects on a host of adaptive anatomic and behavioralĬhanges as hominid fines expanded their range into new habitats. The driving force behind hominid brain evolution (which Washburn, respecting Sir Arthur Keith's influential opinion, equated with increased brain volume) was not simply "selection pressure" created by external environmental change. Movements in ways that favored tool use, were the final catalyst for the subsequent split of humans from the same primate line that had produced the great and the lesser apes much earlier.ģ. Subsequent changes in the upper limb, altering the repertoire of hand
The first-as Darwin himself asserted-was the adoption of a bipedal gait. Two critical modifications in the musculoskeletal system contributed to the launching of the hominid line. Consequently, the behavior of any living members of any species, at any given time, reflects the operatingĬharacteristics of separate parts of the body in general, and (for Washburn), of the brain and musculoskeletal system in particular.Ģ. The brain and the musculoskeletal systems, as organs, evolve just as organisms themselves do, by modification of structure and function over time. Washburn's thesis actually contains three distinct assertions:ġ. Man began when populations of apes, about a million years ago, started the bipedal, tool-using way of life. Interacting complex, with each change in one affecting the other. From the evolutionary point of view, behavior and structure form an From the short-term point of view, human structure makes human behavior possible. It follows that the structure of modern man must be the result of theĬhange in the terms of natural selection that came with the tool-using way of life. Now it appears that man-apes-creatures able to run but not yet walk on two legs, and with brains no larger than those of apes now living-had already learned to make and use tools. This specific assertion was made by anthropologist Sherwood Washburn, writing in Scientific American, just as the first reports of a tool-using hominid (Homo habilis) in East Africa were circulating. At the time of her discovery there had already been a few tentative suggestions that the modern human brain might have evolved as a consequence of the increase in tool use among She was the first anatomically bipedal human ancestor to be discovered,Īnd she had an un-apelike hand and a chimpanzee-size brain.
Twenty years of careful research on her species have solidified her claim to primacy. Sensation not only in the anthropological world but with the public at large. The best known is Lucy, who lived some 3.2 million years ago in Hadar (in eastern Africa) and whose discovery created an enormous THE EARLIEST DIRECT HUMAN ANCESTORS were the australopithecines, "southern apes" of Africa who walked upright. ODD ARRANGEMENTS AND FUNNY SOLUTIONS ARE THE PROOF OF EVOLUTION-PATHS THAT A SENSIBLE GOD WOULD NEVER TREAD BUT THAT A NATURAL PROCESS, CONSTRAINED BY HISTORY, FOLLOWS PERFORCE. BUT IDEAL DESIGN IS A LOUSY ARGUMENT FOR EVOLUTION, FOR IT MIMICS THE POSTULATEDĪCTION OF AN OMNIPOTENT CREATOR. OUR TEXTBOOKS LIKE TO ILLUSTRATE EVOLUTION WITH EXAMPLES OF OPTIMAL DESIGN-NEARLY PERFECT MIMICRY OF A DEAD LEAF BY A BUTTERFLY OR OF A POISONOUS SPECIES BY A PALATABLE RELATIVE. How Its Use Shapes the Brain, Language, and Human Culture
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