The Ancestors we had

Of late, I was reading about different findings and theories around Human Ancestors. I tried to summarize what I found out.

Introduction
Over years human beings believed that human beings are special creation of God and got created at His will. The lack of reasoning and strong believe in divine beings forced human beings to rely on divine theories rather than looking at the nature to find out the laws. Over years, human beings have got rid of those burdens through science and started finding the natural laws. Let us visit where exactly we are in terms of knowledge of Human ancestry.

History of Findings
The first light was thrown on this topic by the famous scientist Charles Darwin. In his book named "Origin of Species", he mentioned how a species can separate it out from other through "Natural Selection" and "Evolution". However, he was not able to explain how the first life on the earth was formed. A contemporary scientist, Gregor Mendel came up with the idea of Hybrids which was later converted to study of Gene and DNA. Although Darwin's findings were widely contested by the Church those days, his theories opened floodgates to a new set of discoveries in the medical science and human genetics.

Darwin's theory - A mere theory?
There are a series of accusitions on the Darwin's theory that it was a mere 'hypothesis' and has proved nothing. Most of the accusitions came out of religionalists, who are threatened as this theory annihilates a long standing interpretation that 'God created the Man'. A lot of scientists even today accuse Darwin's theory to be having 'no evidence'.

However, there are yet to be a proof found that goes against the Darwin's theory. The tools used to evaluate the theory were mostly undiscovered at Darwin's time. More and more the human knowledge is growing, the evidences seem to be piling up in favour of it. For example, the use of RadioCarbon Dating to determine the age, use of Genetics to study inheritence, Comparative Anatomy, Geographical distribution or the Fossil records, all supported evolution. On the other hand, there are no counter-evidences of it are found yet, neither a fossil of a human in Jurassic age nor a specific bacteria which defies the laws of natural selection.

The limitation of the study of evolution is the time it takes to perform an experiment to open eyes. Due to less complexity, the evolution can be observed in the level of microbes and it takes less time. However, in bigger creatures, like a human being, it takes thousands of years to become recognizable to a naked eye.

In short, evolution and creation of species take the same position in the world of science as that of gravity. Gravity can not be proved, it can be observed till date, the same is with Evolution. We are yet to know whether gravitation works on all celestial bodies due to our limited knowledge of the Universe, same with evolution of living beings.

Mitochondrial Eve
Coming back to the human ancestors, the study of ancestors are now powered by Genetics and Molecular Biology. The inductive study on human genetics reveals an important fact. A person directly inherits the mitochondrial DNA directly in his/her maternal line. Male sperm contains only enough mitochondria to power the sperm to the surface of the egg – it does not enter the egg. The egg, however, contains mitochondria that have been passed from mother to daughter for countless generations. The only way for mitochondrial DNA to alter is by natural mutations, which occur very slowly when compared with the almost frantic gene mixing we and our parents take part in. Because the rate of mitochondrial genetic mutation is slow, the mutation difference between the two populations can then be compared, and a 'clock' can be produced, enabling the rate of mutation in mitochondria to be established. The genetic survey that produced the whole Mitochondrial Eve scenario didn't just sample Africans and Europeans – it sampled genes from people all over the planet. When mitochondrial DNA was compared, the survey discovered a startling result. Fundamental similarities in mitochondrial DNA in living humans suggested that we all contain genetic material from a single woman who was living in Africa around 200,000 years ago. The woman is called Mitochondrial Eve.

The confusion
Wilson's naming Mitochondrial Eve after Eve of the Genesis creation story has led to some misunderstandings among the general public. A common misconception is that Mitochondrial Eve was the only living human female of her time — she was not. Mitochondrial Eve is the most recent common matrilineal (female-lineage) ancestor for mtDNA of all humans. She didn't live alone – she would have lived within a community. There is no reason to suppose that she had more than one female child. But there is reason to suppose that whatever female children she had, they contained specific advantages for survival over the rest of the population.

Y-Chromosomal Adam
Similar to women, men inherit their Y-Chromosome directly from their father. In human genetics, Y-chromosomal Adam (Y-mrca) is the patrilineal human most recent common ancestor (mrca) from whom all Y chromosomes in living men are descended. Y-chromosomal Adam probably lived between 60,000 and 90,000 years ago, judging from molecular clock and genetic marker studies. While their descendants certainly became close intimates, Y-chromosomal Adam and mitochondrial Eve are separated by at least 30,000 years, or many hundred generations. Y-chromosomal Adam probably lived 65,000 years ago, and mitochondrial Eve some 150,000 years ago. The people living around the same time as these two individuals would have passed on their genes like Adam and Eve, but their Y chromosome and mitochondrial DNA lines would have eventually died out.

Implications
1) It qualifies as an evidence for Single-origin hypothesis. Again, it has nothing to show that human beings started from a single couple, but to show that human beings originated in a single place through mutation.
2) A milestone in the path of Genetic Genealogy.

Future
It opened a door only to the study of Human genetics and evolution. The religionalists are coming up with Intelligent Design theory, which claims to bridge the religion with the Science. It says that the first instance of life was created by God on the earth, after which the evolution took place. It is true that the creation of life itself has been a point of contention as scientists are yet to create a fresh life in the lab. Let us wait till we can see life to be created in front of us and observe all the phase of Human Evolution inside a lab, open in front of our eyes. I will definitely write up on origin of life very soon.

References
1) The Ancestor's Tale by Richard Dawkins
2) BBC article.
3) Wikipedia articles.
4) MSNBC Page on Genealogy.
5) A simple version of the story.
6) An excellent documentory on Human evolution in this site.
7) Articles on Mukto-Mona.