Apes Swing, Men Walk:
Why canít we swing through the trees like Tarzan?
David A. Adams
Copyright © 1999
It seems that the reason we canít swing through the trees like Tarzan is due to something that happened a long time ago—our branch broke off.
Once upon a time we were in a little band called the proto-apes, somewhere between Aegyptopithecus and D. (Proconsul) africanus. We were all gibbon-sized with strong, flexible arms, hands, and fingers, able to swing, hang, reach, and break our fall after a leap, and our arms were roughly equal in length to our legs.
Over millions of years a species (Ramapithecus-Kenyapithecus) evolved that took to living by preference on the fringes of the forests, returning to a clump of trees at night or constructing simple woven shelters of branches and grass. From the generalized structure of the arm-swinging, erect-postured, mainly arboreal proto-ape, there were two likely lines of evolutionary development—one toward increased power and flexibility of the arms (as in the large apes), and the other toward erect terrestrial bipedalism. Now this is where the branch broke off.
The proto-ape species that was eventually to become man took the latter course; as it became more efficient in killing small mammals for meat, it left the forests for the savannas, where under the influence of quite different selection pressures from those of the forest, it developed its inherited behavior patterns of incipient tool and weapon use, flexible social grouping, and community festivals, into human technology and culture.
The apes that remained within the forest tended toward increased body size (which was paralleled also in the species that led to man) and here is the snapping of the branch—those who stayed to swing developed arms which became structurally longer and more powerful , a tendency that was to continue in all the large apes, in parallel with their less closely related cousins the gibbons from the Miocene onward.
According to Vernon Reynolds in his 1967 book, The Apes, this is the way it all happened. I suppose some of this information has been changed by scientists since that time according to a newer more up-to-date Whoís Who in the old ape-man world, but I would guess that the basic idea is still around.
We just donít have the arms for swinging like the apes. I would guess that Jim Thompson could bring all of this up to the present time, but until your knuckles grow closer to the ground, you are likely to feel more comfortable walking. Farmer is probably correct. With Tarzanís greater muscle and bone size there would have to be some structural compensation for his shorter human arms for him to swing like the apes.
David Adams, just hanging around