Hominid Altitudinal-Latitudinal Adaptations
John Waters (jdwaters@dircon.co.uk)
20 Oct 1996 16:00:05 GMT
It might be thought that terrestrial mammal specie needing to
adapt from an equatorial climatic zone at sea level to a higher
latitude would move north or south as required. However, most
mammal specie do not do this. For good reason.
Any mammal specie needing to adapt to a higher latitude will
need a number of
simultaneous genetic adaptations to meet the basic requirements
of the latitude
concerned.
For example, a mammal specie moving from an equatorial climatic
zone at sea level
to a semi-equatorial climatic latitude, will need to adapt to at
least four different
climatic conditions. These comprise a reduction in average
annual temperature,
reduced humidity, seasonal changes and changes in day length. As
a result, four
simultanous genetic adaptations are required.
However, there is an alternative route to a higher latitude
which would involve fewer
simultaneous adaptions. In this respect, the specie could adapt
first to a higher
altitude on the equator, and then adapt to a higher latitude. In
such a case, a move
from an equatorial latitude to a semi-equatorial altitude would
only require two
simultaneous adaptations. As the semi-equatorial altitude is
still on the equator, the
specie would only need to adapt to a reduction in annual average
temperature and a
reduced humidity level.
When the specie had adapted to the semi-equatorial altitude, it
could then adapt to
the semi-equatorial latitudes. This would only require a further
two simultaneous
adaptations. Obviously, two simultaneous adaptations are far
more likely than four
simultanous adaptions. So the altitudinal-latitudinal adaptive
route is the one taken
by most mammal specie. Hominids would be no exception to the
rule.
It should be noted that Mount Kenya on the equator, has a full
range of climatic
zones ranging from equatorial at its base, to polar at its peak.
When a specie has moved north or south to a higher latitude, it
then spreads east
and west throughout the global climatic zone. Only when the
whole of the latitudinal
habitats are completely populated will there be any need for a
further
altitudinal-latitudinal adaptation.
During global cold periods the latitudinal climatic zones are
moved towards the
equator. The terrestrial specie tend to remain in their
respective climatic zones, so
they also move towards the equator. This creates a population
squeeze in the
equatorial regions - at all altitudes. As a result, it is during
these global cold periods
that the altitudinal - latitudinal adaptations on the equator
tend to take place.
So there is no altitudinal adaptive continuum. Specie will only
adapt to a new
equatorial altitude when they have to. As long as they can
migrate north or south
within the climatic zone, this will be the preferred line of
adaptive migration. As the
global cold periods come at infrequent intervals, the
altitudinal adaptations are
similarly infrequent.
Fossil evidence implies that H. erectus adapted to the warm
temperate altitudes and
latitudes. The general consensus of paeleontological opinion
seems to be that H.
archaic was an adaptation to the cold temperate latitudes, while
H. neanderthal was
an adaptation to tundra latitudes.
If this is correct, it would appear that the colonization of the
tundra altitude and
latitude was the last habitat adaptation. So the question arises
as to the status of the subsequent hominid adaptations. In this
context, it should be noted that an ecological niche is not
solely a habitat. It is also a behaviour. For this reason, there
can be many different ecological niches in the same habitat.
By implication, it would appear that the H. sapiens adaptation
was a behavioural
adaptation rather than a habitat adaptation. If this was so,
then H. neanderthal and H. sapiens would be complementary specie
within the same habitat. This would be
similar to the situation of the Gorilla and Bonobo, which are
closely related specie
inhabiting the same equatorial habitat. A further implication is
that H.ss was also a
behavioural adaptation, this time occupying a complementary
niche in the cold
temperate climatic zone. Here it would share its habitat with H.
archaic.
And so to the questions.
1. Was H. archaic a cold temperate climatic adaptation?
2. Was H. neanderthal a tundra climatic adaptation?
3. Is there any evidence of seasonal migrations concerning
either of the above
specie?
4. Was H. sapiens a behavioral adaptation to a tundra habitat?
Is there any evidence
that it was contemporary with H. neanderthal?
5. Likewise, is there any evidence that H.ss was contemporary
with H. archaic?
6. In view of the evidence of habitat destruction by H.ss, could
this behaviour have
started at the inception of the specie?
John.
John Waters is the author of "Helpless as a Baby",
a book concerned with general and human
evolution. It may be accessed at URL
http://www.dircon.co.uk/jdwaters/HAAB.htm
jdwaters@dircon.co.uk
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