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Re: An alternative to ST and AAT
Holly Reeser (reeser@flmnh.ufl.edu)
Thu, 17 Oct 1996 17:10:13 -0400
Newington Reference Library wrote:
>
> A NEW APPROACH TO THE PROBLEM OF HUMAN EVOLUTION
>
> by Andrew Lewis
>
> The Savanna Theory (ST) and the Aquatic Ape Theory (AAT) both make
> certain assumptions that need to be challenged.
>
> Both believe that our remote ancestors stopped living in one environment
> (the forest) and started living in another (either the savanna or the
> coastline).
>
> Another possibility is that our ancestors evolved to become more
> adaptable, to be able to exploit different environments seasonally. They
> could have moved between at least three different environments to exploit
> the seasonl abundance of each.
>
> When the East African forest diminished, it did not do so evenly. In the
> river valleys the forest remained. Where the river approached the sea,
> the valley became wider and such features as delta formation, meandering
> and braiding allowed for the forest to become more extensive.
>
> I can imagine our ape ancestors becoming concentrated in these valleys,
> especially closer to the sea. Each valley would eventually have become
> an 'island' separated by expanses of grassland. The forest would have
> continued to provide food for the apes, but only at certain times of the
> year. It would have become more seasonl compared to the rain forest that
> still exists in West Africa. At other times of teh year, the apes would
> have gone hungry.
>
> They would have ventured out of the valley in search of food. Sometimes
> they would have moved along the coastline. Sometimes they would have
> moved on to the savanna and the savanna-mosaic. In time they would have
> learned and remembered when each environment offered the best resources
> in each season, and seasonal patterns of movement were established.
> Rivers and lakes, swamps and mud flats are also possible food sources.
>
> Chimpanzees and bonobos are the most adaptable of animals apart from man.
> Our ape ancestors were adaptable, and we developed this even further.
>
> Three qualities made us so uniquely adaptable
> 1. Our behaviour became even less dependant on instinct and more
> dependant on learning and reason.
> 2. We were omnivorous.
> 3. We developed physiological adaptations that allowed us to exploit all
> three different environments.
>
> The greatest physiological changes we needed to make were those
> which allowed us to exploit the coastline environment, because that was
> the environment that was the most different from that of forest-living
> apes.
>
> That is why it seems as if most of the differences between apes and
> humans can be explained as aquatic adaptations.
>
> We have lost specific adaptations to forest life, such as curved finger
> bones that assist in gripping branches.
>
> Our loss of forest-specific adaptations and our gain of aquatic
> adaptations is misleading. It leads us to believe that our ancestors
> left the forest and moved to the sea. I believe that we evolved to
> become good all-rounders. We never 'left the forest', not altogether.
> Humans have good tree-climbing abilities, especially in parts of the
> world where such qualities are useful, and children all over the world
> love to climb trees.
>
> My theory disposes of the need to think of an 'aquatic phase' that ended
> as man abandoned the coast to live inland. I believe that the coastal
> regions of East Africa have provided the site of human evolution from the
> time of our ape ancestors up to recent times.
>
> When Europeans started to sail around the world 500 years ago they found
> people living by the sea and from the sea wherever they went. If our
> remote ancestors stopped living by the sea, when and why did they return
> to become the ancestors of Polynesians, Strandloopers, Tierra del
> Fuegans, etc.? Surely it is more reasonable to suppose that some humans
> have always lived by the sea, at least for part of the year. The fact
> that other humans lived in the interior does not alter this.
>
> The presence of early modern humans at Klasies River Mouth in South
> Africa, clearly living from the sea, supports this.
>
> Population increase in a successful species such as our own would mean
> that not everyone could live in the prime location of a river estuary.
> They would have to compete, and the losers would have to learn to live
> with a less than ideal environment. We were adaptable enough to be able
> to do this. In this way the interiors of continents were colonised, with
> rivers and the Rift Valley being settled first.
>
> This would mean that modern humans have more aquatic adaptations that any
> of our ancestors. We have more aquatic adaptations than the archaic Homo
> species, who in turn had more aquatic adaptations than the
> Austalopithecines. If the 'aquatic phase' theory is true then the
> opposite would be the case.
>
> The study of mitochondrial DNA suggest that all humans alive today
> are descended from a small group of people living in Africa perhaps as
> little as 100,000 years ago. I suggest that they evolved on the
> coastline of East Africa, not the interior.
>
> My own theory solves such problems as why have humans never re-evolved
> fur. If a naked skin is unsuitable for a savanna existence, and so would
> not have evolved on the savanna, why did it remain when our ancestors
> supposedly went to live on the savanna full time? All humans have
> maintained the physical type most suitable for existence in several
> different environments.
>
> My theory does not depend upon a dramatic change in climate to explain
> our evolution. Our increase in adaptability is merely a continuation of
> ape and especially chimpanzee adaptability. Therefore my theory is not
> challenged by recent new information, suh as the fact that our ancestors
> became bipedal well before East Africa became drier and savannas spread.
> A small increase in the seasonality of the forest, together with more
> variation in habitat, would be enough to favour ever more adaptable apes.
>
> Also, difficult questions for AAT, such as
> 1. Was there enough time for our remote ancestors to have evolved an
> aquatic way of life during an 'aquatic phase', considering possible time
> scales?
> 2. Why would an aquatic ape want to abandon the aquatic way of life for
> the savanna?
> are not a problem for my theory.
>
> Several people have suggested that AAT and ST are not mutually exclusive
> eg. john Gribbin, Jeremy Cherfas and Sarah BM Kraak. My theory is an
> elaboration of this.
>
> It is only natural to think that each species of animal has one
> environment to which it is adapted. However, many species are adaptable,
> eg. the elephant. Elephants can live a semi-aquatic lifestyle in a
> suitable environment, and they can also live in near desert conditions
> where the may have to migrate long distances. They are long-lived,
> social and intelligent, just like us.
>
> I do not regard my theory, which I call the Multi Habitat Theory (MHT),
> as a contradiction of AAT. It agrees with it on one point, that many of
> the differences between man and ape are aquatic adaptations. I realise
> that there is as yet no proof for it, but there is also no proof for AAT
> and especially ST. The more information we have, the more we realise the
> need for an alternative to ST: I believe my theory makes a contribution
> to the debate.
What East African sites are coastal? Off the top of my head I cannot
think of any coastal Australopithecine or early Homo coastal sites.
And how will you test this?
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