ZKEA

Emerging Diseases : Biological Terrorism : Biological Warfare

Summary

Mankind is a member of the extended family of Hominidae. Besides humans, this family includes bonobos, chimpanzees and gorillas. All of the species in Hominidae arose in Africa, in a long line stretching back to African primates over 40 million years ago. Thus mankind's roots in Africa go back very far indeed.

About 5-10 million years ago the genus Homo diverged, along the evolutionary line that led to humans. During the course of the following millions of years a diverse set of hominid species proliferated in Africa and left plenty of fossils. However compared to some of evolution's better efforts, such as cockroaches, these hominids were never very successful. Although brainy compared to the rest of creation, they were also big, slow and clumsy. In addition, judging by the teeth-marks left on innumerable fossils, they were also quite tasty. These hominids had no natural defenses against predators save for their wits. And apparently wits often came up short against anything possessing big enough teeth and claws.

Ice-ages came and went. The hominids struggled, succeeded modestly for a while, and then slowly diminished. Generally prospects were not looking so good for the hominid side. Even so they kept spinning off new species, looking for that golden recipe that would ensure success.

About 200,000 years ago yet another new hominid species emerged. These were the archaic Homo sapiens. Basically these hominids were us, albeit with a few primitive features scattered here and there, such as a fondness for rap music. This new species was tall, dark-skinned and hairless, and physically feeble even by the undemanding standards of the hominid group. True, they possessed an exceptionally large brain, but they had little else to recommend them. Therefore Homo sapiens often joined their hominid cousins in the scattered bone heaps that littered the landscape. Large cats, in particular, really enjoyed the company of our early ancestors. Why not? We were fat and tasty, could not run very quickly, and we made such amusing noises when cornered.

But then the Homo sapiens got their big break. About 70 thousand years ago, give or take, mental complexity passed a key threshold. Somewhere, somehow, a mental switch was thrown and a completely new dynamic emerged. This new dynamic was culture. Like the invention of life billions of years previously, the invention of culture gave its possessor invincible power and advantages.

Suddenly, in a geological instant, mankind invented complex art. Cave walls that were previously bare spawned an astonishing array of drawings. New ideas flourished and were transmitted with incredible speed. Weapons that were previously bare and strictly utilitarian suddenly sported artistic flourishes. Clothing became popular, as did clothing lice. The rate of technological innovation massively accelerated. Concurrently, highly symbolic artifacts were created that clearly had significance beyond that of everyday living. Often these artifacts were even interred with those dead bodies. In fact, for the first time, for mysterious reasons that must have boggled the mind of every other species on the planet, great care was now taken in disposing of the remains of newly-deceased Homo sapiens. This was unique behavior not seen in any other animal.

Because of these and other adaptations, mankind was ecologically invincible. He left Africa in waves of migration, populating first Asia and Australia, and then later Europe and the Americas. In a short period of time we left our African cradle and became a global species.

This rapid change led to some unforeseen results. In particular, because of mankind's long association with Africa, other species in the region had ample time to co-evolve with our species. For example, prey animals in Africa learned long ago that humans were bad news. They adapted and, among other things, learned to greatly fear our hunters. Thus prey species in Africa were usually able to survive our presence, despite countless thousands of years of relentless hunting pressures. A similar thing happened in the world of microorganisms and parasites. Because Homo sapiens roots stretched deeply into the African past, these species had a long time to adapt to our presence. Gradually they moved in and set up residence in our bodies, fine-tuning their adaptations to exploit this new ecological niche (us).

These two preceding evolutionary facts explain two curious outcomes that occurred when human beings finally left Africa.

First, early humans were very healthy. This is because we largely left our diseases and parasites behind. These were adapted to the African environment and so many of them could not migrate with us. Thus early migrants to the other continents tended to be relatively disease-free. It took a long time for these diseases to "catch-up" and follow us into these new habitats, or for new localized diseases to evolve.

Second, prey animals that humans encountered outside Africa had no time to adapt to this new super-predator called Man. As a result humanity devastated the large fauna wherever they went. A wave of extinctions followed the migrations of early man. Scores of large species were wiped out due to our hunting prowess.

The first fact became very pertinent in modern times. Again, because of Homo sapiens long habitation of Africa, the overall environment is tuned to biologically exploit us. The pathogenic load in Africa is therefore very high relative to the rest of the world, and further, there were many other pathogens that were primed to cross over into our population should circumstances warrant it.

As modern Africa became more populated and urbanized, therefore, this situation became more acute. This problem has been exaggerated by absolute poverty, poor government and a and rapidly-deteriorating general environment. These environmental and demographic stresses are much more severe than found on the other continents.

For these reasons Africa is an epicenter for historic and newly-emerging diseases. Two historical examples are smallpox, which probably evolved into our species during the Old Egyptian period and malaria which probably spread from its West African origin about ten thousand years ago due to the advent of agriculture.

The classic modern example, of course, is HIV, which apparently crossed over into a small group of Africans in the 1950s and then went on to kill millions of people . However, other diseases, such as Ebola and Marburg fever have also made scary forays into our species. As the environmental situation in Africa becomes more acute, we can expect more emerging diseases of this sort.

Link: River Blindess (Onchocerciasis)
Link: Malaria, AIDS and Evolution In Africa
Link: Hominid Evolution (Short Summary)
Link: Tracking Evolution of HIV-1
Link: The Evolution and Genetics of Malaria Resistance