In article <>, engelking at earthlink.net (engelking at earthlink.net) writes:
>I am a left-handed person and I have been recently reading up on the
>causes of my handednes.. Many of the reports I have read conclude that it
>is caused by either trauma to the brain at birth, it is genetic, or that
>it is a form of brain damage (!). What is the status of all these theories
>in the medical community? And also, do we left-handed people have any
>special right brain skills (visual-spatial I've read?)? What are the
>consequences of being left-handed? How do I differ from right-handers?
>>>Thanks,
>engelking at earthlink.net
The problem of dextrality (right-handedness) goes much deeper than
the assumed accident of brain-damage producing the contrary
sinistrality (which is only a possibility to be considered among
others).
Our ancestors Homo erectus, were dextral like ourselves
(Poulianos 1977,Anthropos 4 p147, Schick & Toth 1995 pp140-142 for
two kinds of evidence), but other great apes show no similarly
strong preference for one hand or the other - why? It could be a
genetiic bias or social or both in the long term of evolution.
Among primates in general 50/50 ambidextrality is the rule,
although some deviant bias appears in a few chimpanzee troops,
especially among Pan troglodites who are habitual tool-makers. But
their deviation is nowhere nearly as great as ours. We can
therefore take it as given that the bias is predominantly a social
effect, although possibly not 100% so.
Certainly the social continuity that operates through
conscious and unconconscious teaching tends to obscure any genetic
element in the matter, especially in our own species with its
elaborate education structure. The strength of social bonds among
Homo erectus 1.7 Myr. ago is attested the diseased skeleton
KNM-ER 1808 to have been far stronger than exists among non-human
hominids today. This female would have been unable to feed
herself due to the disease (hyper-vitaminosis A) yet was kept
alive for many months, probably year, by her kin. (Walker and
Shipman, 1996, Chap. 8)
There is therefore a case for there being a selection
pressure that could operate opportunistically on either social or
genetic processes (Gray, 1979, Anthropos 6 p128) to produce the
human bias for dextrality as it exists. Tracking these down is
probably more difficult than finding a brass needle in a hay-stack
(no magnets possible!).
Bibliography;
Poulianos, A.N.(1977) Anthropos 4 (1-2) pp 147 - 151
Schick,Nicholas, and Kathy D. Toth, "Making Silent Stones Speak"
Simon & Schuster. Weidenfield & Nicholson 1993
Walker, Alan, and Pat Shipman,"The Wisdom of Bones" - Chapter 8
Knopf - 1996.
Gray, G.K., (1979) Anthropos 6 pp 128 - 135 "The Neurophysiology of
Dextrality"
Photocopies of the material from "Anthropos" are available
by snail from:
The Anthropological Association of Greece at
Dafnomili 5,
ATHENS 11471,
GREECE,
Tel. (Greece, Athens,) 36 10 251
If any difficulty contact me by email
