Savanna Fantasts
- From: Marc Verhaegen <m_verhaegen@xxxxxxxxx>
- Date: Sun, 09 Mar 2008 12:52:43 +0100
Thermoregulatory selection pressures and savanna chimpanzees:
climatological data from Assirik, Senegal
LF Marchant, WC McGrew, CEG Tutin & PJ Baldwin 2008
"One prominent evolutionary model for human origins in the Pliocene involves
thermoregulation, that is, adaptive response to heat stress. Hominins
ranging over tropical landscapes dominated by grasses and deciduous, open
woodlands faced strong solar radiation."
What "hominins" are they talking about??
They *assume* our ancestors were savanna dwellers!
"Proposed adaptive responses to these evolutionary selection pressures
include bipedality, hairlessness, sweating etc. (Wheeler 1994)."
These people still live in the middle ages:
Wheeler's nonsense have been demolished years ago:
"... The savannah theory thus remains an artificial construction, a ?Just So
Story¹ comparable with the hypothetical ?land bridges¹ in geology before the
theory of plate tectonics. Accounts of how our Plio-Pleistocene ancestors
may have lived on the savannah include
- bouts of strenuous activity outside the gallery forest for hunting or
digging (Hanna & Brown 1983),
- dogged pursuit of swifter animals over one or two days (Carrier 1984),
- bipedal trekking after migrating herds of savannah ungulates (Sinclair
cs.1986).
Some of the even more imaginative versions appear mutually contradictory,
eg, the hypothesis of a foraging or hunting male accords ill with the
meridian theory of Wheeler that our ancestors became bipedal to minimise
direct solar radiation at midday and retained a hairy heat shield only on
top of the head (1984, 1988, in imitation of DHK Lee,in Newman 1970 & in
Schmidt-Nielsen 1974:89). If we accept this reasoning, it must have been the
women who ranged over the plains at noon while the balding and bearded males
rested in the shade." :-D
"Detailed climatological data for sites with other large-bodied hominoids
living in similar environments are lacking. Here, we present 13 data-sets:
maximum & minimum daily temperatures in gallery forest, open woodland &
short grassland; hourly average temperatures (07.00-19.00 hr) & humidity in
forest, woodland, grassland & unshaded grassland. These were collected over
4 annual cycles at Mt.Assirik, Niokolo-Koba Nat.Park, Senegal, during a
field study of wild chimpanzees Pan troglodytes verus. Daily
max.temperatures averaged monthly never fell below 30°C, and average daily
minimum temperatures rarely fell below 20°C. Mean daily maximum temperatures
were highest in grassland, lowest in forest, intermediate in woodland, but
mean daily minimum temperatures did not differ across habitat-types.
Hour-by-hour daytime temperatures differed similarly across habitat-types,
with unshaded grassland being even hotter, especially in dry months after
annual bushfires. Average humidity showed a reverse pattern, being
consistently higher in forest vs.woodland vs.grassland, at all hours of
sunlight over the annual cycle."
Nice work, but totally irrelevant to human evolution.
"In sum, hairy, large-bodied quadrupedal apes cope with heat stresses"
Hairy perhaps, yes.
"comparable to those likely to have been faced by Pliocene hominins."
:-D
.
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