New research has proved the single origin of humans theory by combining studies of global genetic variations in humans with skull measurements across the world.
The research, at the University of Cambridge and funded by the Biotechnology and Biological Sciences Research Council (BBSRC), represents a final blow for supporters of a multiple origins of humans theory.
Competing theories on the origins of anatomically modern humans claim that either humans originated from a single point in Africa and migrated across the world, or different populations independently evolved from homo erectus to home sapiens in different areas.
The Cambridge researchers studied genetic diversity of human populations around the world and measurements of over 6,000 skulls from across the globe in academic collections. Their research knocks down one of the last arguments in favour of multiple origins. The new findings show that a loss in genetic diversity the further a population is from Africa is mirrored by a loss in variation in physical attributes.
Lead researcher, Dr Andrea Manica from the University's Department of Zoology, explained: "The origin of anatomically modern humans has been the focus of much heated debate. Our genetic research shows the further modern humans have migrated from Africa the more genetic diversity has been lost within a population.
"However, some have used skull data to argue that modern humans originated in multiple spots around the world. We have combined our genetic data with new measurements of a large sample of skulls to show definitively that modern humans originated from a single area in Sub-saharan Africa."
The research team found that genetic diversity decreased in populations the further away from Africa they were - a result of 'bottlenecks' or events that temporarily reduced populations during human migration. They then studied an exceptionally large sample of human skulls. Taking a set of measurements across all the skulls the team showed that not only was variation highest amongst the sample from south eastern Africa but that it did decrease at the same rate as the genetic data the further the skull was away from Africa.
To ensure the validity of their single origin evidence the researchers attempted to use their data to find non-African origins for modern humans. Research Dr Francois Balloux explains: "To test the alternative theory for the origin of modern humans we tried to find an additional, non-African origin. We found this just did not work. Our findings show that humans originated in a single area in Sub-Saharan Africa."
Source: Nature, 19 July 2007. Vol. 448 Issue 7151 pp 346-348
Comments
Then those disparate populations became diverse over time is another.
How are they contradictory?
Hank Campbell | 07/18/07 | 11:12 AM
I know where I came from. The flood nevertheless. Makes every
body in the world your at least your eighth cousin!!!
Anonymous (not verified) | 07/18/07 | 11:28 AM
Moreover, if the last common ancestor of all living humans had really lived in 1700, as your claim implies, that would mean that in every generation every person would have had to have more than 10 children who survived to reproduce. While large numbers of children were not uncommon in the 18th-19th centuries, rarely did that many of them survive, and even more rarely did all of those get to reproduce themselves (monasteries and the army took care of that).
Moreover, 300 years is not enough for the genetic diversity observed today to emerge, and we have trustworthy historical records from which we can infer that a genetic diversity of comparable magnitude existed already thousands of years ago. All of this refutes your claim of universal human eighth-cousinship. In fact, the last common ancestor of all humans living today lived in prehistoric times, and some people are only umpteenth cousins.
Anonymous (not verified) | 07/19/07 | 12:11 PM
andy (not verified) | 07/18/07 | 11:28 AM
The article also confuses the distinction between the conflicting theories of single origin and multiple origins by not always making clear reference to geographical origin or ancestral origin.
All those flies (not verified) | 07/18/07 | 21:49 PM
Anonymous (not verified) | 07/18/07 | 22:08 PM
But now you restate (as the article stated) that diminished diversity within geographically separated populations implies (proves) a common origin. Could not disparate origins also give rise to the same diminished diversity and to the same separation of populations? After all, distance and time to travel from A to B are putatively the same as from B to A, and time to develop enroute or subsequently is the same everywhere. Maybe what's missing from the argument are the premises that a certain small part of Africa is where it all started and that it contained but one source point. Even so, what's to disprove multiple source points within even that small part? (I use the word "point" figuratively.) Because the article doesn't say, one must assume that the two premises are taken for granted, and because I don't understand that these premises are sufficient to prove the conclusion, I'm having trouble formulating any sort of syllogism that makes sense.
In short, the article is not as well written as your responses to my complaints! Thank you for your clarifications and for the pleasure of reading your responses!
All those flies (not verified) | 07/19/07 | 06:58 AM
If I read this right, it's saying that different populations evolved from homo erectus. Does that make homo erectus "one source"? The apparent contradiction of terms makes the logic hard for me to follow. Likewise, it's counterintuitive to think that homo sapiens became less diverse as we spread out from Africa, but that's what the article asserts without comment. Take it one step further: decreasing diversity associated with distance (and presumably time) from Africa implies that the source homo erectus was extremely diverse. That makes it "one" source?
Darn! Where did all these flies come from? Why, from mommy and daddy flies.