Science & Non-profit

The lust for grip-pressure, an instinct to carry tools over greater distances

grip-pressure, Australopithecus, Homo erectus, tool,use, arboreal, bipedal, human evolution.

It is my theory that the lust for grip-pressure, an instinct that prevented the Australopithecus from falling out of the trees by making him hold on to the branches, made Homo erectus carry his tools and thus enabling the reuse of these tools over far greater distances than before. This put a much higher fitness benefit on the production of better tools and making the lust for grip-pressure one of many reasons for our brain size to increase.

drs. Geert Poelman (http://www.Geert.com).
Geert Poelman, April 27-1999, written in July 1994.

Introduction

Environmental changes have always been one of the main causes for evolutionary change and our own evolutionary history seems to be no exception.

Until about eight million years ago our common ancestor, with the chimpanzee (Pan sp.) and the gorilla (Gorilla gorilla), lived in one homogeneous biogeographical province on the African continent. At which time, through tectonics forces, a rift was formed that divided the original region in two. The West remained humid with forests and woodlands and the East became ever dryer and evolved into brushwood savannah (COPPENS, 1994). This spread this ancestor over many new niches and lead to its simultaneous divergence into three separate lines (ROGERS, 1993).

The niche in which our ancestor, later known as Australopithecus, found himself was that of brushwood savannah and one of its features is that the shielding canopy has gone. This allows much higher levels of solar radiation to reach the ground, exposing the animals living in this niche to high levels of heat and water stress (HORIZON, 1994).

The anatomy of the Australopithecus together with our knowledge about its niche leads us to the inevitable conclusion that its life style required it to be, as adapt in climbing trees, as in walking and standing bipadely (RAK, 1991), (SPOOR et al., 1994). This means that it must have mostly fed and lived in and beneath small trees and bushes where it still common for today's chimpanzees to take a bipedal feeding posture. In fact it was shown that for chimpanzees, the fruit diameter and tree height are the critical factors eliciting bipedalism (HUNT, 1994). However, as chimpanzees have not adapted their anatomy for bipedalism, there must have been a secondary force that made bipedalism a necessary strategy.

Calculations on the thermal stress as well as the fact that chimpanzees actively avoid exposure to the direct sun when it is warm, show that there was a niche for kind of chimpanzee that could cope with the high degree of thermal stress in the savannah. One of the tricks Australopithecus used to do this was bipedalism, as this strategy can greatly reduce heat and water stress. (Hominid thermoregulatory adaptations (HORIZON, 1994), (PORTER, 1993), (RASCH et al.,1991), (RUFF, 1991), (WHEELER, 1984), (WHEELER, 1985), (WHEELER, 1991a), (WHEELER, 1991b), (WHEELER, 1992a), (WHEELER, 1992b), (WHEELER, 1993), (WHEELER, 1994)).

The second and last part of this tale again begins with a change of climate leading to evolutionary changes.

About 3.3 to 2.4 million years ago, the whole earth cooled and eastern Africa became even dryer. The niche of brushwood savannah with Australopithecus made place for that of grassy savannah with a new species now known as Homo erectus. Judging on the anatomy, it was even better adapted to cope with thermal stress and it's bipedal- as well as its arboreal- capacities must have been as good or as bad as our own. Hunting on its sheer strength of thermal endurance it must have quickly fanned out over the world as a 1.8 million year old specimen was found in Java (Indonesia) (SWISHER et al.,1994).

What's new

Hunt's observations showed that 74% of all chimpanzee arboreal bipedal behaviour was aided with support from their hands (HUNT, 1994). It is quit logical that the chimpanzee as well as the Australopithecus, that were both climbing flimsy little trees in a bipedal fashion, had some instinct that made them hold on with their hands for stability as much as possible. Now let me define this instinct, that I will call the lust for grip-pressure, as the apparent need to exert pressure to the hand in such a way as if one was holding a branch in a small tree. This instinct is still functioning well in humanity today, as anyone who watches us will soon notice. It is even quite likely that, while reading this paper, you yourself are in some way exerting pressure on the palms of your hands or within the grip range of your fingers.

Now two more thoughts. One, you can't walk on all fours or climb trees and carry tools at the same time, you must first discard of them. And two, the lust for grip-pressure will, unlike in the bipedal case, be for filled by the action of climbing or walking itself.

Now my theory is that although Homo erectus was a good biped, his lust for grip-pressure was still functioning well and made him carry his tools that for filled this lust, over far greater distances and thereby enabling their re-use. Making the investment put into making these tools far more prosperous than before and thus putting a much higher fitness benefit on the production of better tools. In this way, I suspect, the lust for grip-pressure was one of the many reasons for our brain size to increase.

Acknowledgements

I would like to express my thanks to drs. Bekenkamp who was my gifted and inspiring high school teacher and with whom I tried to write this article before I had left school. This however floundered on my then article writing skills.

References