By Bhatki Patwardhan
It seems that, after a long time of excited discovery and research, the topic of ancient humans and paleontology has reached a close. We all know about ancient humans: how they evolved from Africa, then migrated out, and then created societies. The history of the world made it quite clear, I guess. But actually, that train of thought, as the still-active and flourishing field of paleontology proves, may be oversimplifying things a bit. But before exploring several of these discoveries, we must explore the theories we started from. And before exploring the theories we started from, it is interesting to look into how scientists collect data to create these theories in the first place.
The scientific methods behind data collection
To place excavated fossils, scientists have to extract DNA from them. According to biology and environmental science teacher Kyle Jones, living tissue deteriorates in fossils leaving behind only protein, and it is rare for scientists to find even a couple of intact cells in a skull or bone. But fortunately, scientists need only one cell! The whole DNA code is found in one cell, and scientists can use a modern genetic engineering technique, PCR, to amplify the sequence until they have thousands and thousands of copies at their disposal. These can then be compared to other databases—scientists are currently working on creating a database full of genomes for every organism, just as they did for humans (which was the human genome project). It is an ambitious project indeed, and will certainly improve our knowledge drastically.
The Out-Of-Africa Theory
Now, on to the theories that scientists started out with. As National Geographic tells us, most scientists agree that about 200,000 years ago, Homo Sapiens, developed in Africa. Then, climate changes forced them to the Middle East, to Asia, to Australia, and then to Europe,.
But actually, there were not just homo sapiens wandering around. There was a huge and diverse family of different primates. Some textbooks and sources try to arrange this in a chronological line, which each type evolves to the next one, until the most well adapted, most perfect Homo Sapiens were formed. But while this is very flattering, as Britannica.com acknowledges, it is completely false. The different types of primates were very close to modern humans as we know them: our evolution, just like any other organism’s evolution, has been a work of trial and error.
“The homo sapiens were simply the branch that lasted the longest in time,” Jones said. “[We are] the last surviving twig on a vast and intricately branching bush, rather than the sole occupant of a summit that has been laboriously climbed and, by extension, somehow earned.”
There were five main groups of ancient humans, and most textbooks and sources list them chronologically: Homo habilis, the first identifiable human-like apes (mostly found in Africa); Homo erectus, in whom our upright spinal cord could be first seen; Neatherlanthals, the human species closest to us; and finally, the Homo Sapiens, which some scientists narrow down even further into Homo Sapiens Sapiens to signify the most modern humans.
The Two-Way-Ticket-From-Africa Theory
The arrangement of this list gives the impression that the Homo Erectus came first, then Neatherlanthals, and so on, and then the Homo Sapiens hiked out of Africa. But that is where two articles published last year (on Ancient Origins and the Science Magazine) starts fogging the mirror. An incredibly ancient skull found in China (called Dali, ) dates a mind-blowing 200,000 years ago, first classified as an Homo Erectus. This astonished scientists, since it clashes with the theory that humans were still in Africa then. That is exactly what these articles disprove: it appears that there was more than one out-of-Africa event, and these events did not just involve Homo Sapiens, but subspecies far, far older.
While scientists at first classified Dali as Homo Erectus, they actually realized that he was a Homo Sapien, but very close to the Erectus. Such similarity between the two types was surprising, since scientists had predicted that it would be closer to the Neatherlanthal, which chronologically should be the development stage between the Erectus and Sapiens. The fact that an entire “development stage” had been skipped was incredible. Even more incredible was the fact that “[scientists] expected Dali to exhibit similarities only to other Chinese specimens, particularly the ones that came before it (Homo erectus) and after it (Homo sapiens). But it ended up being more similar to these fossils from North Africa and the Levant.” This indicated that, firstly, the chronological “levels” of development were a myth: all ancient humans of both older and newer types were there at the same time and place, and interbred a lot. Secondly, the fact that the skull does not resemble other Chinese ones indicates, astonishingly, that some human traits may have developed outside of Africa and then brought back in: gene flow may have been multidirectional.
So far, we have explored how much more complex, chaotic, and random human evolution really was than what was earlier believed. Really, the only thing that has remained the same about the chronological out-of-Africa theory is that scientists do believe that the first identifiable humans did appear in Africa before anywhere else.
But now, even this idea might be under fire. On the island of Crete, scientists discovered 9.7 million years old teeth and footprints which belong to a type of hominin only known to have existed in Africa 4 million years later. Now, the land masses were arranged very differently, so all this may be mean is that the geographical range of our early ancestors was much, much wider than thought. It may also mean that the traits which the fossils indicate evolved several times before becoming permanent. But all things considered, the article states that there may even, however slight, be the possibility that the out-of-Africa theory is wrong.
Considering the dispersion of genetic diversity, fossils, and other evidence, this is a very extreme and perhaps a mistaken conclusion. Depending on what scientists find, the out-of-Africa theory may be discarded entirely, and a new location may be considered the “Cradle of Humanity.”
Relevance of this information today: Ancestry DNA tests
Several of us may have seen the youtube videos in which people give DNA cheek samples to an ancestry test, and figure out where their ancestors are from, and what percentage of different geographic/ethnic groups they are. Technologyreview tells us that there are two ways these groups use DNA testing to determine your ancestry. The first is the dad test: they track y chromosomes along family lines, since the genes on this particular chromosome rarely change; or the mom way, which is tracking mitochondrial DNA (which is passed only from the mother). Mutations in these two types of DNA also remain constant, and as Jones confirms, they are unique and can be used to track your ancestors back thousands of years.
But should everyone take these tests (even in an alternate universe where the prices are reduced)? Jones cautions against it. It is, as he says, a special new technology which has at yet no use except track people’s ancestry, but it is new.
“After all, we do not know what ancestry.com is going to do with that extensive database that they have” Jones said. “There is always a risk involved with trying new things for the first time. With something like this, I would prefer to wait until we know more. Your DNA is literally the instructions to make you… it is in a sense the most personal information about you”
Jones does assure, though, that there is not much chance of this information being widely misused.
If there is something to learn from history and from previous scientific discoveries, it is the danger of oversimplifying and jumping to conclusions. this must be kept in mind especially while researching and making conclusions about human evolution. Many of us have a natural curiosity about human evolution, its progress, and the locations where it happened. But we must remember that many things do not, and should not, be generalized to a single source, place, or origin. Just as there is no one cradle of civilization, there may not be any one cradle of humanity. Just as all cultures, civilizations, and fields are composites of many widespread and diverse influences, so is human evolution a complex network of interactions, developments, and traits. It is a way to recognize the contribution and value of every time, every place, and everyone.