the ignorance concerning genetics and lack of reading comprehension is strong here

tomatoes didn't triple in size it was their genome [that's you chris the fish]

the way scientists "know" is the same way they know we have neanderthal genes
[unless you're a sub-saharan afican]
the same way they know michelle O has white ancestors

by examining and analyzing the genes

Where do you really come from? And how did you get to where you live today? DNA studies suggest that all humans today descend from a group of African ancestors who—about 60,000 years ago—began a remarkable journey.

The Genographic Project is seeking to chart new knowledge about the migratory history of the human species by using sophisticated laboratory and computer analysis of DNA contributed by hundreds of thousands of people from around the world. In this unprecedented and of real-time research effort, the Genographic Project is closing the gaps of what science knows today about humankind's ancient migration stories.

The Genographic Project is a multi-year research initiative led by National Geographic Explorer-in-Residence Dr. Spencer Wells. Dr. Wells and a team of renowned international scientists and IBM researchers, are using cutting-edge genetic and computational technologies to analyze historical patterns in DNA from participants around the world to better understand our human genetic roots. The three components of the project are: to gather field research data in collaboration with indigenous and traditional peoples around the world; to invite the general public to join the project by purchasing a Genographic Project Public Participation Kit; and to use proceeds from Genographic Public Participation Kit sales to further field research and the Genographic Legacy Fund which in turn supports indigenous conservation and revitalization projects. The Project is anonymous, non-medical, non-profit and all results will be placed in the public domain following scientific peer publication.