common view about the emergence of our bipedal ancestors is, that
their habitat in woods diminished and transformed into a savanna.
Our ancestors were then forced to move from tree to tree covering
ever greater distances, carrying foods and babies.
That is a central opinion among anthropologiists that this lead to
bipedalism, a creature specialised in hunting, running after prey,
His fur was shedded, because running produced excess heat and nakedness
meant easier transmission of this heat.
Or, it was a useful adaptation for getting rid of parasites.The head
did behold its hairy cover to protect it for equatorial sunburn
and overheating of his precious brain.
But; there is no other animal adapted to a life on the savanna without
a fur. The nakedness is a negative feature as ultraviolet radiation
is not filtered and the transpiration to cool the body is a major
source of losing water. We are fairly good runners., yes, but much
slower than any of the
savanna herbivores and the predators that catch them. Not to mention
that running upright in the open field is a most stupid way to chase
as every hunter can tell you. Above that the big predators would diminish
the then pre stoneage, pre Homo spec. ancestral groups.
The ability to run for long distances is a feature, that fairly recently
has been under selective pressure in special areas;
the Tarahumara indigenes in the Mexican sierra are known for their
ability to run for days and Ethiopian and Somalian runners hold most
Olympic medals in marathons.
In the Homo litoreus theory, bipedalism was not forced upon us by
a savannah like habitat, but the effect of isolation on possible archipelagos
with most food to collect in
shallow coastal waters.
This start of bipedalism is to observe as the wading of the proboscis
monkey Nasalus of Borneo.
The vertical orientation is also a good adaptation to swimming
clip of wading
and swimming proboscis monkeys
Chimps and gorilla's do the
same thing when the cross a brook or river. Whilst wading the body
is lifted by upward pressure, but the forward movement in water
takes more force , far more than on the land. You sure have noticed
this yourself in a swimming pool or on the beach.
litoreus view about our ancestors is that they were at any time
forced to adapt to wading, being trapped on an archipelago where seafood
but other foods were sparse.
And when sea levels lowered, these bipedal humanoids could easily go
on their walkabout along the coastlines of continents, crossing natural
channels and estuaries
by swimming or rafting. Plenty of driftwood around in those days.
Walking and running on dry land is then a secondary specialisation. The rapid dispersion of mankind around
the world is easily explained this way.
Maybe the inborn xenophobia of men accelerated this process:
the ways of Kain and Abel mentioned in Genesis stick with us....
It is possible, that this scenario
unfolded itself more than once; once for Australopithecus, then with
H. erectus and later with H. sapiens.
In that case, the basic toolkit of Homo was put under heavy pressure
for the survival of the direct ancestors of H. sapiens.
Once " freed" from their supposed trap on islands, this "pressure
cooker enhanced toolkit" and the brains that came with it gave them
a new kick start.
Of course this is all speculative, but it deserves real attention.
Based on DNA (not totally compliant with archeological evidence).
Click to enlarge
For a credible account of the possible influence of sea level fluctuations
on human evolution,
read The InterGlacial Island Hypothesis formulated
The relation as depicted
by R. Little
Look up the different major fossil finds in the human lineage,
check if their ages fit with the figures given in "The InterGlacial
Island Hypothesis" by plotting periods
of low sea
levels (Y) against age of fossil finds (Y)
Female Gorilla wading
(2005) Wild Gorillas Handy with a Stick. PLoS Biol 3(11): e385
The naked ape Shedding
the furHaving a fur is not very
suitable for a creature that has to enter and leave the water all
the time. It leads to a
strong cooling effect as you can find out for yourself participating
in a 'wet t-shirt' contest. Shedding fur and applying
subcutaneous fat as insulation is the solution to this problem.
fat is an adaptation quit often found in aquatic homoitherm animals,
like penguins or seals. If you are adapted in this
way and change your life stile conquering the land you do encounter
a problem; you cannot get rid of excess heat and have to use
evaporation heat to cool your body core. that means transpiring a
do have "internal" fat around their organs and in their abdominal
cavity, just like other mammals and birds.
About half of the ten to twelve kilograms of fat in average man is
subcutaneous. To keep things simple, it is convenient to use this
15% of the weight of a given person is fat and half to one third of
that mass is subcutaneous. this goes for rather skinny
and for (not to) obese people.
There is however a notable difference between men and women.
If you want to test this rule, you can investigate it yourself , using
an apparatus to measure skin fold thickness.
See for instance http://www.brianmac.co.uk/fatcent.htmA
model experiment is possible to test this idea. You just have to use
a few empty PET bottles filled with warm water to represent the body
woolen socks as 'fur' and pure vaseline as 'subcutaneous fat'. in
this model you can stick to 1 kg water (body core) being insulated
by 0,1 kg vaseline.
You can cover the fat bottle with plastic kitchen foil (= skin)
With a thermal sensor inside connected to a computer, it is possible
to compare cooling and heating of the "body core" PET bottles under
This has to be done in three settings; submerged and in air. In air
add the difference of a dry fur (sock) and a wet fur.
Construct your own models and design a feasible experimental setting.
set up your central question and hypothesis and go for it.In
the process you may possibly think
of better options that serve this purpose.
- Prepare three bottles: 1 blank,
1 with al woolen stocking as felt and 1 with vaseline surrounded
with cling film
- Use water of 40 ° C to start
- Put thermosensor in every bottle
connected with receiver
- Place dry bottles in an airstream
(blower) = savanna
(repeat to keep them damp) bottles in airstream = beach
in cold streaming water = water
Prepare a complete report on this assignment. Example of "kitchen table" version .
Infrared radiation or parasites?
transpiration humans do have a second way to lose excess heat; a dense
network of capillary vessels directly under their skin.
If the body core temperature rises above 37° C. these vessels are
filled with blood and lose heat as infrared radiation. The other way
that the bloodstream towards the skin (and the extremities) is closed
down, when the core temperature is lower then 37° C. This transition
s realised rapidly,
as to be expected for an in-and-out-of-the water lifestyle. On a hot
savanna, only able to hunt and forage by day because sense of smell
and hearing are underdeveloped, this system is contra productive,
a sure way to become overheated.
The effects of this can be demonstrated with a "blank" bottle
in the depicted experiment (that you did insert in the experiment
if you did it correctly).
Blood in the capillary vessels is flowing on the outer side of the
subcutaneous fat; a direct link between a overheated core and external
a scientific point of view, these experiments ar far to simple, but
the essential features of the proposed relations can be demonstrated
There is enough evidence from different fields of physiological research
to justify this. For
bipedalism and hairlessness there have been made other suggestions
by different scientists.
Three I will mention here and you have to give your arguments on the
question if they are plausible or not;1.
Walking upright diminishes the surface area of the body exposed to
direct sunlight, an idea welcomed as a good suggestion among paleoantropolgists.
Q; How many hours a day Is the position of the sun right above your
head on the African savannah? Use geographical information.
Q; Find out about the way baboons are moving and relate this to the
statement in 1. 2.
With a fur there is always the problem that parasites like to procreate
Shedding our fur is the obvious solution. Also accepted as a reasonable
Q; How many species of mammals on the savannah did the same?
By P. wheeler, John Moore University Liverpool.
3. Walking upright was an adaptation of humans to carry babies. See
walking tall to carry a baby
Q; Who are the better runners; females of males?
Q; As far as we can observe nowadays; how do people with a Neolithic
and nomadic lifestyle carry their babies?
Female baboon with young GNU free
Readings on bipedalism
for a related experiment on humans.