Anyone who is interested in family history, or anyone who has ever gone to a library or archive to undertake genealogical research knows that while the subject is an exciting one, the work can be tedious and the resulting picture often fuzzy.
This is where we stand with regards to family research writ large, that of modern humanity. To be sure, we have come a long way since we humans even became aware of the fact that we had a very long history, or a deep ancestry. Consider the day, now more than 180 years ago, when people went into a cave in Belgium and encountered remains later identified as belonging to a Neanderthal individual. Compare that against our current understanding of human evolution. How we got here is an interesting story and it is an interesting tale to relate,. Where we go from here is equally intriguing.
Here is part one: how did we get here?
Traditionally, we rely on three main sources of information when studying human origins, our origins. These sources are: the material remains of that past (including both fossil remains and man-made tools), genetics and comparative primatology. The latter refers to observation of current non-human primates and possible correlations between their habitat and behavior with the environment in which our ancestors once lived and their behavior. If there is one constant in the picture generated by these sources is that it is always being refined and updated. Such is the nature of scientific endeavor: it never stands still. Thankfully, our thirst for greater understanding is never slaked either. There is always more to investigate.
Material remains have been the backbone of paleoanthropological studies. After all, what could be a better illustration of human evolution than a fossil of an ancient ancestor, or a tool made by a distant relative of ours? By carefully plotting where these remains have been found, we can reconstruct a picture of human evolution, we can start to see where our earliest ancestors once arose, evolved and eventually migrated from. By studying their tools, we can see human inventiveness at work. At first this is a tediously slow process, but eventually we see it picking up pace to the point we are today: new gadgets developed on a daily basis.
For a while, as people were studying fossil human remains, others were investigating genetics. However, initially the practitioners of these two pursuits did not know of each other’s work, or, did not realize how their work could benefit from the other person’s insights. And so we see how Mendel and Darwin were contemporaries, but their respective scientific insights and breakthroughs did not cross over and inspire the other.
|photo credit: ynse|
Our genetic makeup is the result of millions of years of evolution.
Since the Human Genome Project was completed in 2003, we have learned a lot about our genetic makeup. Since then, the chimp genome, gorilla genome, and the orangutan genome have been finished; by the way, the latter was sequenced in our own backyard here in Houston. This provides a nice platform to start comparing our genetic makeup with that of our close primate relatives, and find out where we differ, and, more interestingly, how similar we are below the surface. It turns out we are quite similar.
The difference 1% makes.
Differences, no matter how ostensibly small, remain important. One can be in awe about the fact that we share around 99% of genes with chimps. One could also turn that around and say “See how much difference 1% makes?” That difference, in turn, may help us figure out when in time we started to go our own way, after the split from a common ancestor. This is where the notion of a molecular clock comes in. This concept has been used to “to investigate several important issues, including the origin of modern humans, the date of the human/chimpanzee divergence, and the date of the Cambrian explosion.”
Thus we see in the literature that orangutans, with whom we share around 97 % of our DNA, split from the family tree around 16 to 15 million years ago. Humans and chimps became their own branches on the family tree around 6 to 5 million years ago.
As one researcher recently put it: “There remain signals of the distant past in DNA, and our approach is to use such signals to study the genetics of our ancestors.”
The concept of the molecular clock continues to be refined as our understanding of its potential and limitations has grown. For better or worse, however, it provides us with a tool to help situate major branching events on the family tree. This brings us to our own immediate past, our place in history, when modern humans appeared on the scene.
Discoveries made in East Africa date the emergence of modern human beings to about 200,000 years ago. Two skulls, found in 1967 in Ethiopia were recently identified as the earliest known modern humans. While that makes all of us Africans, it data from mitochondrial DNA have suggested that our ancestors did not make it out of Africa until 60,000 years ago. The archaeological record seems to disagree, however. Man-made tools twice that age have recently been found in the Arabian Peninsula.
It is at times like these, when dates provided by genetics and archaeology diverge, that we hear voices criticizing the invalidity of this approach. What we will see happen, however, is that this apparent disjunction between two sets of data, will spur on researchers to find where the source of this disparity lies and resolve it. Were that to be impossible then we would have to go back to the drawing board and rethink our ideas about human evolution and the timing of critical events related to it.
Now for part two: where do we go from here?
As people become more mobile, we are now finding our mates much further away than we did just a few generations ago. This means that it will become more difficult to check that box on the census form asking for our ethnicity. It also means that we are slowly becoming more homogenized. Indigenous cultures are disappearing and language follow suit.
To get an idea of how exhilarating and mind-boggling this pursuit of science can be, I would like to invite the reader to attend an upcoming lecture.
On March 7, the Houston Museum of Natural Science will host Dr. Spencer Wells, lead scientist of the Genographic Project.
His lecture, entitled “Deep Ancestry: Inside the Genomic Project,” is brought to us by the Leakey Foundation. Dr. Wells is an Explorer-in-Residence at the National Geographic Society and Frank H. T. Rhodes Class of 1956 Professor at Cornell University. Dr. Wells will share with us how the Genographic Project, using data from hundreds of thousands of people, including members of the general public, the Genographic Project is deciphering the migratory routes followed by early humans as they populated the Earth.
I look forward to this lecture, and hope to see many of you at the museum that evening.
In the meantime, a pop quiz.
Q: What do the following individuals have in common?
|Brazilian indian chiefs, Kaiapos tribe, during a collective interview.
Left to right: Raony (state of Mato Grosso), Kaye, Kadjor, Panara (Pará)
photo credit: Valter Campanato, Agência Brasil (ABr). April 17, 2005
|Ethiopian Orthodox Christian woman – Lalibela, Ethiopia
photo credit: Dirk Van Tuerenhout
|Lake Titicaca – Uros people
photo credit: Dirk Van Tuerenhout
A: They are us. We are them. This is us.