Understanding human evolution

Dr. Swarkar Sharma
The intriguing thought “How we Humans originated” has always fascinated mankind and to solve this mystery of Human origin, we had come up with various believes and stories. With the advent of various scientific tools, a new perspective to this quest was added. Direct sources of information about our past are the fossil records, the remains of the skeleton. Exploiting Paleoanthropology i.e. combined study of ancient fossils with respect to existing Species, evidences generated that suggested modern human originated from ape like ancestors, and have evolved over a period of approximately six million years ago. Our ancestral cousins are gorilla and chimpanzees and sufficient scientific evidences exist suggesting Human and chimpanzee lineage separated about 6-7 million years ago. In due course of the quest, it was discovered that our early progenitors lived in the African continent than anywhere else and ancestors to present day humans (modern human) originated in Africa. From Africa ancestors of modern humans migrated out, to populate the rest of the world widely accepted as “Out of Africa model” of human origin and migration.
Genetics is a field of biology that helps us understand heredity. Passages of characters from parents to offsprings are controlled by pieces of DNA called genes that are inherited. Mother and Father contribute equally this content and children subsequently inherit it to next generation. During course of inheritance in time from one generation to another many a times some changes arise in DNA, which are called mutation or variations and are inherited to the next generation. These variations can have negative or positive impact as they may affect function of a gene. This affect can cause a disease or can be beneficial by helping in adaptation to environment and better survival. Apart from these some variations have neutral impact as they donot affect the function of gene.  Scientists exploited this and used DNA as a tool to understand Inheritance and find relationship amongst different species. Studying DNA of individuals from across the world populations, and based on sharing of variations one can figure out how much two individuals are related. This has given rise to a new technological branch called Phylogenetics that helps to understand our deep in time ancestry and thereby giving us a new way to look at how we modern humans originated and migrated out of Africa. Dating back to ancestors using variations as markers through generations reveals about evolution history and genealogy of man. The approach is revolutionary in exploring the history of human and is called “coalescent theory” that relates ancestors based on the same set of variations two individuals share. To trace generations, the variations inherited together by present generation are contrasted back. These contrasting lineages when merge back in time results into the emergence Most Recent Common Ancestor (MRCA). The hypothesized Maternal MRCA of all the people living today is called ‘Molecular Eve’ and paternal MRCA is called ‘Molecular Adam’, estimated to have lived about 140-200 million years ago.
The exact reason for human migration “Out of Africa” is yet not clear but it had been been estimated that there was a dramatic change in the climate, ‘The Ice Age’ which would have made the life of ancestors difficult, as genetic evidences prove that Human population during this period was decreased up to 10,000. This ice age could be one of the factors for the move of the ancestors to find the better shelter for living. Two main routes purposed for the migration of humans and their dispersal across the globe are: the “coastal route” or “southern route” of migration from the horn of Africa over southern Arabia, followed by migration along the Indian coastline to Australia, estimated to have occurred ~60,000- 75,000 years ago and “northern route” suggested to have occurred around 45,000 years via the Levant corridor of Africa leading to eastern Asia through steeps of central Asia and southern Siberia. It is interesting to note India has served as a major corridor in the dispersal of modern humans as it is positioned at the tri- junction of Africa, Northern Eurasia and oriental region. The very first wave of Humans migrants from Africa through southern route have passed through India and many of those ancestral groups elected to stay in India and their descendents are represented as “Onge” tribe in Andman Island. Since then, various migrations have been speculated and along with cultural evolution resulted in diverse Indian population groups. Presently, India is agglomerated with 4635 anthropologically well-defined populations having 532 tribes, 72 primitive tribes and 36 hunters and gatherers population groups.
Jammu and Kashmir (J&K) State of India is an excellent geographic location in Himalayan region that might have acted as corridor or incubator of various human migrations from Eurasia. There have been indications in literature that these areas have human signatures very deep in time. J&K has a unique distinction of possessing modern, medieval and ancient history and rich Archaeological data. The State of J&K has 3 divisions: Jammu, Kashmir and Ladakh and further divided into 22 districts. J&K population is highly diversified and is constituted of many strictly endogamous population groups distributed among 5 major religions: Hindu, Muslim, Sikh, Boddhist and Christians. The role of Jammu and Kashmir has never been assessed at the genetic level in view of its strategic geographical location, difficult mountainous terrains, as well as valleys that may have acted as doorways to Central Asia from the Indian Subcontinent.