HUMAN EVOLUTION IN BRIEF.

 Life appeared on the Earth about 350 crore years ago in the most rudimentary form, as a cell and the first organisms were Bacteria.

In 1936 the Russian Biochemist A.I.Oparin has propounded the theory that life originated by Chemical evolution. This theory stood with time and later could be proved in the laboratory 1953 when the 4 amino acids, Adenine, Guanine, Cytosine and Thymine, the basic strands of DNA could be synthesized. It is today accepted by a large majority of scientists.

Then, Earth was not what it was today. It was much hotter and filled with Methane, Ammonia and Water vapour. Our Sun continuously emits Ultraviolet rays which would completely destroy all life on earth if they reach the Earth. Today we are protected from this deadly radiation by the Ozone layer in the atmosphere, but there was no Oxygen on the earth then and therefore no Ozone. So it would have been impossible for any form of life to exist on the primordial earth then. Then after sometime, due to the ultraviolet radiation and the numerous lightning blasts occurring on account of the heavy cloud cover of water vapour; Methane, Ammonia and water vapour reacted with each other and combined to form the Amino acids which are the building blocks of the DNA and therefore life. This theory was proved by the Stanley Miller experiment.

All animals have been named under the binomial nomenclature. The first word of the nomenclature denotes the “Genus” and the 2^nd the “Species”. All of you know this.

I am giving below a table showing the evolution of humans from their ancestral species.

CLASSIFICATION OF MAN

KINGDOM	ANIMALIA
PHYLUM	CHORDATA	Evolved 540 million years ago. Animals with backbone.
CLASS	MAMMALIA	Evolved 66 million years ago. Animals that suckle their young.
ORDER	PRIMATES	Evolved about 85-55 million years ago. Proto primates like Tree Shrews and Tarsiers and Squirrels. These are adapted to living in tropical forests with large brains, visual acuity, color vision and altered shoulder girdle and dexterous hands.
FAMILY	HOMINIDAE	Separated about 14 million years ago from Primates. Contains 8 extant species. 1. Orangutan (3 species), 2. Gorilla (2 species) 3. Chimpanzee (2 species) 4. Humans. A common ancestor of all these lived 14 million years ago.
SUB FAMILY	HOMININAE	African Hominids
TRIBE	HOMININI	Includes Humans, Chimpanzees and Bonobos. The Bonobo is similar to the Chimpanzee but is a separate species.
GENUS	HOMO	Evolved from Hominidae 2.5-3 million years ago. It consists of Australopithecus which evolved into various species. It started with Homo Habilis.
SPECIES	SAPIENS	This is our species that evolved about 300,000 years ago. This started evolving from Homo erectus about 500,000 years ago and crystallized 300,000 years ago. All other species in the Genus Homo except us have died out.

 

Between the ORDER of PRIMATES, and the FAMILY of HOMINIDAE is the INFRAORDER SIMIFORMES. This infra Order contains both Monkeys and Apes. The ancestors of humans at that time were similar to apes only and are combined in this infra order.

Our Genus Homo started with Australopithecus about 2.5-3.0 million years ago in East Africa. It then separated from its Tribe named Hominini which includes Chimpanzees.

Next to come in after Australopithecus was Homo Erectus, which was a species of the Genus Homo. This came into being about 2 million years ago. It had a human like gait and body proportions. It is also the first human species to have exhibited a flat face and a prominent nose. It is the first animal to walk erect.

This evolved into various species of man. Firstly, African population of Homo Erectus has given rise to many species. Homo Heidlebergensis (ancestor of Neanderthal man), Homo Antecessor, Homo Denisova, Homo Neanderthal and finally the modern humans. The Asian Homo Erectus evolved into Homo Floresiensis and Homo Luzonensis. The time of disappearance of Homo Erectus (last identified was Solo man from Java) was about 110,000 years ago. Thus the species of Homo Erectus existed for almost 2 million years which is a very long time for us. 

Our species the Homo sapiens is the only species currently living in the Genus Homo. It evolved at about 300,000 years ago. Since Homo Erectus was alive till 110,000 years ago that means our ancestors and the Homo Erectus (including Neanderthal man) lived on the earth at the same time. Yet all other species of Homo Erectus became extinct leaving us all alone in our Genus. Why so we do not know?

Thus the evolution of man which started with Chordata 540 million years ago took so much time to evolve into our species 300,000 years ago. 300,000 years is like just yesterday in Earths chronology.

Our species is so young, yet in such a short span it has managed to dominate the planet like no other species had done. What is the reason for this phenomena we do not know? Yes it is intelligence that made us supreme, but why did some other species too not develop intelligence and why our species alone?

The first city humans ever built was Jericho which dates back to 9000 BC. So for almost 290,000 years of the existence of our species, we did not develop any higher civilizations, but it took us just 10,000 years to dominate all other species and virtually rule the earth.

Now going ahead would humans destroy themselves? To me it appears very much probable. We already have Nuclear weapons and we cannot even imagine what weapons humans would further develop in the future. The rapid development of our race had undergone seems to be pushing it to the edge. In the process we not only endanger ourselves, but also endanger all other species on the earth. Would the human race survive? We can only speculate on that and hope that wiser counsel would prevail on our race in the future.

Forget about Monkeys and Apes, it is unbelievable to think that further back, we had a common ancestor with Tree Shrews, Tarsiers and Squirrels.  They also belonged to the ORDER PRIMATES and our ancestor separated from them only between 55 million and 14 million years ago.

Of course if we extend our ancestry back further, we would land at the first single cell that had evolved on the earth. That is an unbelievable fact which actually shocks us. That way, each species of animals and even plants that have evolved on the earth is related to us.