"CONTINENTAL DRIFT AND CONCURRENT
EVOLUTION OF HUMAN SPECIES"
The theory in vogue about man’s origin is that he first evolved in Africa and from there spread out to colonise the rest of the world. This theory is known as the Out-of-Africa model, and also as the Recent single-origin hypothesis (RSOH), Replacement Hypothesis or Recent African Origin (RAO) model.
After leading the multi-disciplinary Gondwanaland Expedition across the interiors of 17 countries of South Asia, West Asia and Africa, through regions of great significance in the evolution of flora, fauna and humans, I doubt this theory and am more inclined to support the hypothesis that different races of humans, like many plant and animal species, evolved independently in various parts of the planet.
The fact that most of the oldest hominid fossils have been found around the Great Rift Valley lakes of Africa cannot make us decisively conclude that man originated in Africa. Perhaps older hominid fossils exist elsewhere in the world waiting to be discovered. Or, if they ever existed, these fossils have not been preserved by nature and are lost to science.
Fossils are more readily found in the African Rift valleys due to the layers of sediments and protective volcanic ash that help preserve them. Key records of human ancestry have been found along the Awash and Omo Rivers of Ethiopia, at Lake Turkana in Kenya, and Olduvai Gorge and Laetoli in Tanzania. At Hadar, in Ethiopia, river erosion exposed the site where Lucy, one of the earliest known hominid, walked between three and four million years ago. Great Rift geology in this Afar region of Ethiopia is ideal for creating fossils. It is a low area that collects sediments necessary to bury and preserve bones. There is also volcanic ash that allows scientists to date the sediments. Faulting along the rift helps by bringing old bones back to the surface where they can be found. But just because the oldest hominid fossils have been found in regions, where ideal conditions exist for their preservation, it cannot be concluded that man originated in Africa.
Even if we are to assume that man did originate in Africa, what was the motivation for him to leave his homeland and migrate across inaccessible forests, deathly deserts and wide oceans and seas to lands and islands thousands of miles away? From the early stage of hominid evolution to, say, 50,000 years ago, when the hunter-gathers settled down to an agrarian life, the population was small, food abundant, and wars had not graduated to more than a bar room brawl, there was no reason or necessity for our ancestors to risk venturing from Africa to as far away as inaccessible Australia and all the places in-between.
If man migrated out of Africa and colonised the rest of the world, then other forms of life – plants, trees, ants, termites, butterflies, bees, crows, sparrows, hummingbirds, larks, lizards, bats, rats, squirrels, porcupines, horses, tigers, wolves – and everything else – can also be said to have made a nomadic exodus from the “home continent” of Africa and populated the planet without getting their feet wet.
Animals and humans do not wander unnecessarily. In fact, their instinct always leads them back to their “home”. Birds have a definite migratory path they follow year after year. An Arctic Tern flying to Antarctic from its breeding ground in Iceland will not stray or divert its flight path to Asia or South America. The central population of endangered Siberian Cranes winter in India – year after year – and go back home. Fish have their definite breeding grounds. The Olive Ridley Turtle comes back to the same beach to lay its eggs. Recently in India, a leopard, relocated 400km away from its home, found his way back to his forest. The Bushmen of Africa or the pygmies of Brazil or the Jarawas of Andamans have not picked up their bows and arrows and migrated to pleasanter climes – but have remained firmly rooted to their homeland – in spite of disease, droughts and floods.
It may be observed that traces of the Negroid race, outside of Africa, are in Australia- Papua New Guinea (Aborigines), Philippines (Aeta and Batak), Sri Lanka (Vedas), India (Sentinelese, Onge and Jarawas). Traces - because most of these original tribes inhabiting these lands have either been decimated or have mixed with other migrating races over the recent millennia. The remaining original tribes are marginalised and are on their way to extinction. But observe that these original inhabitants, of Negroid stock, are in countries and continents that were once a part of the super continent of Gondwanaland – that comprised of Africa, Australia, India, South America and Antarctica. Did they all walk from Africa or could they have evolved independently? If the Negroid race could have evolved in Africa from mammals – then could the same mammals not also evolve into the Negroid race on the landmasses of South America, Australia-Papua New Guinea and India - that were once joined to Africa and shared similar ecosystem and ancestral conditions? Reason and Darwinian logic says it should be possible.
Let us have a look at plant, marine and animal life that existed when Gondwanaland broke away from Laurasia - mostly during the Jurassic period, 210 million to 140 million years ago (MYA).
The 'highest' life forms living in the seas were fish and marine reptiles. The latter include ichthyosaurs, plesiosaurs and marine crocodiles, of the families Teleosauridae and Metriorhynchidae. In the invertebrate world, several new groups had appeared, such as: planktonic foraminifera and calpionelids, rudists, a reef-forming variety of bivalves; belemnites; and brachiopods of the terebratulid and rinchonelid groups. Ammonites (shelled cephalopods) were particularly common and diverse.
On land, large archosaurian reptiles remained dominant. Great plant-eating dinosaurs (sauropods) roamed the land, feeding on prairies of ferns and palm-like cycads and bennettitales. They were preyed upon by large theropods (Ceratosaurs, Megalosaurs, and Allosaurs) - all of them belonging to the 'lizard hipped' or saurischian branch of the dinosaurs.
During the Late Jurassic, 160 million to 140 million years ago, the first birds evolved from small coelurosaur dinosaurs. In the air, pterosaurs were common.
During the Jurassic period, arid conditions had eased and the warm, humid climate allowed lush jungles to cover much of the landscape Conifers were the most diverse group of trees and constituted the greatest majority of large trees.
So when Gondwanaland began to break up in the mid- to late Jurassic (about 167 million years ago) there was sufficient plant, marine and reptile life on the super-continent. East Gondwana, comprising Antarctica-Madagascar-India-Australia, began to separate from Africa during the Middle Jurassic. South America began to drift slowly westward from Africa as the South Atlantic Ocean opened, beginning about 130 MYA (Early Cretaceous). East Gondwana itself began to be dismembered as India began to move northward, in the Early Cretaceous (about 120 MYA). As the slow process of rifting and drifting continued, and the continents moved away, the existing life forms would also have moved away with the landmasses (and not fled enmasse to the African part) and continued to evolve there, adapting to the changing climatic and physical conditions.
Flowering plants, spread during this period, aided by the appearance of bees; The first representatives of many modern trees, like figs and magnolias, appeared. Conifers continued to thrive. Insects began to diversify, and the oldest known ants, termites and some lepidopterans appeared – as did aphids, grasshoppers, and wasps. In the seas, rays, modern sharks and teleosts became common. Marine reptiles included ichthyosaurs in the early and middle of the Cretaceous, plesiosaurs throughout the entire period, and mosasaurs in the Late Cretaceous. Baculites, a straight-shelled form of ammonite, flourished in the seas. The Hesperornithiformes were flightless, marine diving birds that swam like grebes. Globotruncanid Foraminifera thrived.
On land, mammals were still a relatively minor component of the fauna that was dominated by archosaurian reptiles, especially dinosaurs, which were at their most diverse. The mammal-like reptiles, or Therapsids had first appeared about 285 million years ago near the beginning of the Permian, which is well before the dinosaurs. They evolved quickly and many different groups arose. The first mammal may never be known, but the Genus Morganucodon and in particular Morganucodon watsoni, a 2-3 cm long weasel-like animal whose fossils were first found in caves in Wales and around Bristol (UK), but later unearthed in China, India, North America, South Africa and Western Europe is a possible contender. It is believed to be between 200 MYA and 210 MYA. However Gondwanadon tapani reported from India on the basis of a single tooth in 1994 may be an earlier contender for the title, with a claimed date of 225 MYA. These early mammals were small, insectivorous, nocturnal, hairy and warm-blooded. Warm-bloodedness is believed to have first evolved among the cynodonts, a late but successful group of mammal-like reptiles from which the mammals evolved. The cynodonts were the only mammal-like reptiles to survive to the Jurassic (200 MYA-145 MYA); in fact they nearly made it into the Cretaceous (145 MYA – 65.5 MYA), and definitely coexisted with many of the major dinosaurs. During the Jurassic the mammals remained small and mainly nocturnal, living beneath the 'metaphorical' feet of the great dinosaurs. These early mammals were more like small monotremes and probably laid eggs. Marsupials and placental mammals (cats, dogs, you and me) did not evolve for another 70 million years.
The age of mammals got underway in earnest during the Cenozoic era, most recent of the the three classical geological eras that covers the period from 65.5 million years ago to the present. During this period, India was further broken into the Madagascar block and the Seychelles Islands. Elements of this breakup are nearly coincident with the Cretaceous-Tertiary extinction event that wiped out about 50% of all species on the planet, most notably the dinosaurs, 65 million years ago. All these species dying out left huge niche vacancies in the habitat. Following this disaster it was the mammals alone of the remaining groups of animals who diversified to take advantage of this new situation. The continent of Australia-New Guinea began to gradually separate and move north (55 million years ago), and, eventually, adjacent to South-east Asia; Antarctica moved into its current position over the South Pole; the Atlantic Ocean widened and, later in the era, South America became attached to North America. India collided with Asia between 55 and 45 MYA. By now, in the last 15 million years since the “Cretaceous-Tertiary extinction event”, the remaining 10 mammal families (five became extinct with the dinosaurs) expanded to become 78 families by the early Eocene, 55 MYA. The number of genera increased from about 40 to over 200 during the same time.
By the middle of the Eocene (45 MYA) all the major groups of mammals alive today had come into existence, though not necessarily as we know them now. By and by, from the life forms and mammals that inhabited the breakaway continents, emerged the primates. The order Primates consists of two major suborders: the Prosimii and the Anthropoidea. The prosimians, meaning, “pre-monkey” were the first to evolve. Often called the "lower primates”, they include the lemurs and lorises.
So, 45 MYA there were lemurs and other prosimians in Africa, India, Madagascar, Eurasia and North America. These evolved, slowly over the next 30 million years, into more advanced primates – like monkeys that populated all corners of the world, displacing most prosimians. The various species of primates, adapting to their own environment, formed their own peculiar physical characteristics. One group of lower primates increased in size – producing the first apes of which the orang utan and gibbon survive in Asia, and chimpanzee and gorilla in Africa. A branch of these apes gave up their arboreal life for the ground. Their larger brain size led to an increase in learning and beginning of a group culture; the manipulative hand and the coordinated eyes made possible the manufacture and use of tools. It was this branch that eventually became the ape-man – around 5 MYA. It had taken 15 millions years for apes to transform to the ape-man. It took the body of one branch of these ape-men another three million years to adapt to the life on plains. “Their feet became more suited to running, lost their ability to grasp, and acquired a slight arch. The hips changed, the joint moved to the centre of the pelvis to balance the upright torso. The skull changed. The jaws became smaller and the forehead more domed. The brain doubled in size” (Life on Earth, David Attenborough). The ape-man gradually became Homo erectus, the Upright Man.
From the above it is seen that when Gondwanaland broke, or for that matter when Pangea broke into Laurasia and Gondwanaland, there were certain forms of life on earth. If from this life, Homo erectus could have evolved in Africa, over millions of years, why then, from the same life forms, could he not also have evolved on other continents that had a similar ecosystem and ancestral conditions? One branch of an orang utan could have evolved into an Asiatic Ape-man who also eventually stood upright and developed Mongoloid features (Java Man, Peking Man) – today’s yellow race of Chinese, Japanese, etc. The African primates and gorillas branched off into the African Ape-man – that evolved into the present Negroid race that further evolved independently in the southern continents that were all once a part of the supercontinent of Gondwanaland. A branch of another primate in Europe, now perhaps extinct and so far untraceable, could have evolved into a European Ape-man – that eventually evolved from Cro-Magnon into the Caucasian race.
Monkeys, in various forms, evolved independently in different parts of the world. They did not walk from Africa to other continents. However, proponents of ‘single origin’ theory believe that they did exactly that – not walked but rafted! Take, for instance, the origin of monkeys on the continent of South America - a matter of much debate. Given the isolation of South America for a large time during the Tertiary Period (65 million – 1.8 MYA), the question of how the monkeys reached the continent is difficult to answer for some scientists. The South American continent became separated from Africa during the Mesozoic era (251 MYA – 65MYA), so the problem is how did the primates reach the continent. The first fossil primates were found in the late Oligocene (34 – 23 MYA) and South America was not much closer to either Africa or North America as it is today. The early thinking by scientists was that the primates rafted from North America to South America, but based on “new evidence” they point to a probable African origin.
The “evidence” showing an African origin of the platyrrhine monkeys of South America is, first, the ocean currents of that time would have facilitated a crossing from Africa to South America and not from North America (Tarling, 1982; cited in Fleagle, 1988). During the middle Oligocene there was a large drop in sea level that may have allowed rafting to be more permissible (Fleagle, 1988). The first fossil platyrrhine, Branisella boliviana was found during the late Oligocene, so it is possible that platyrrhines first came to South America during the middle Oligocene (Fleagle, 1988). Also they point to a morphological characteristic that links the platyrrhines with the Oligocene parapithecids of Africa. Both the parapithecids and extinct and extant platyrrhines show extensive postorbital closure, which is not found in primates from North America (Fleagle and Kay, 1997). The caviamorph rodents that are found in South America also did not appear until the Oligocene and have their closest relatives as the African porcupines showing that there may have been other animals rafting from Africa to South America (Hoffstetter and Lavocat, 1970; cited in Fleagle, 1988). Thus most of the evidence for the origin of platyrrhines points to the continent of Africa (Fleagle, 1988).
It is difficult to believe that the South American monkey rafted across the high seas from Africa. It is more likely, and perfectly plausible, that the South American monkey, rodent and porcupine, said to be relatives of the African species, had their common evolutionary origin in Gondwanaland. They evolved independently in South America from the same base material that was available in Gondwanaland – when Africa and South America were joined as one landmass.
Or take the case of the African and Asian elephants. They are also distant cousins. But did the African elephant also take the raft across the Sea of Tethys? No raft of that period would have the capacity to do so – and Noah wasn’t born yet. Both animals evolved from the same ancestor, a small, trunkless, pig-like animal that lived in Africa. As India moved away from Africa, this pig-like animal evolved into the Asian elephant on the India landmass and as the African elephant on the African landmass, each having its own peculiar characteristics.
Similarly, the primates evolved independently on the separated (but once joined) continents – and, by and by, these evolved into the biologically-similar hominid race with different physical characteristics – the races in the now separated Gondwanaland region assuming similar Negroid physical uniqueness and the hominids of Laurasia assuming Caucasian and Mongoloid characteristics.
Today, the Negroid races survive mostly in Africa. In the rest of the former Gondwanaland regions, the Negroid race has become marginalised, inter-mixed or extinct – Aborigines in Australia-Papua New Guinea, Veddas in Sri Lanka and the Great Andamanese tribals in India.
Take the case of India. I hypothesise that the hominid race that originally evolved in India had Negroid features – their remnants being the Sentinelise, Jarawasas and the Onge on Andaman Islands. At one time, when their population was significant, they had occupied large tracts of the country. As groups of technologically superior Dravidian people, themselves of mixed ancestry, moved into the Indian heartland from the north, 6,000-8,000 years ago, some of the original inhabitants were liquidated – by war and disease. Then, overtime, the original Negroid race mixed with the Dravidian race – the remnants of which probably are the present-day tribals of India, the adivasis, which include Gonds and Bhils of Central India, Bonda of Orissa, Birhor of Bihar, Cholanikan of Kerala, Chenchu of Ap, etc. The Dravidian migrants, who flourished in India for thousands of years and built great civilisations (that reached their peak in Mohanjodaro and Harappa 4,000– 4,600 years ago - around the same time when the Egyptian civilisation was at its zenith), were later themselves pushed southwards by the invading Aryans. Migration and racial mixing between Aryans and Dravidians followed – and is still continuing. Meanwhile, the handful of the remaining original Negroid population, confined to a few small islands in the Andaman Sea, faces extinction.
Evolution is a slow process. It took hundreds of millions of years for apes to evolve. It took another fifteen million years for the ape to become ape-man. Two million years passed before the ape-man could stand upright and become Homo erectus. Homo sapiens emerged 200,000 years ago. According to the ‘Out of Africa’ theory, man moved out of Africa 60,000 years ago. When he moved out, he must have had Negroid features. Are we to believe that in only 40,000 – 50,000 years the Negroid race evolved into Caucasian and Mongoloid races with vastly different physical characteristics?
The proponents of the ‘Out of Africa’ theory are increasingly seeking support of genetics. According to their hypothesis, all 7 billion people alive today have inherited the same Mitochondrial DNA from one woman who lived in Africa about 200,000 years ago; and all men today have inherited their Y-chromosomes from a man who lived 60,000 years ago, probably in Africa. Genetics, as a science, is still in its infancy and the theories and conclusions of geneticists and molecular biologists are, as much as that of other scientists, still vulnerable to revisions, rifts and reversals. For instance, in the last 50 years molecular biologists have been obsessed with the DNA and dismissed the neglected RNA as a a humble carrier of messages and fetcher of building materials. Now, suddenly, they have discovered RNA’s great significance in the evolution of life.There are still several genes whose functions are unknown. Scientists’ ideas about humanity’s past are particularly prone to change, sometimes coming full circle. Forty years ago, for example, palaeontologists thought that hominids, the group of primates that includes modern humans, had been distinct from other apes for some 25m years. The figure has now been revised to 5 million. The certainties about our past are at best transient.
My hypothesis is similar to what is believed by the “multiregionalists” who think “either that pre-sapiens hominids were all a vast, interbreeding species that gradually evolved into sapiens everywhere, or, against all Darwinian logic, that Homo sapiens arose independently in several places by some unknown process of parallel evolution.” (Economist, December 20, 2005). My hypothesis, by linking the continental drift theory and the theory of evolution, attempts to explain this “unknown” process – and does not defy Darwinian logic.