February 4, 2014
About 200 college students at the American Museum of Natural History opened their mouths Monday night and swabbed their cheeks for DNA analysis to trace their ancestry back a staggering 200 thousand years. In the process, they’ll even find out what percent Neanderthal they are. The students, who participated in The New York City Student Ancestry Project, with the City College of New York, may be lucky (or unlucky) enough to find out which thousands of people they can genetically consider their relatives.
Analysis of the student’s genome will also allow them to follow the pattern of their ancestors’ migrations from region to region; in many cases, from continent to content, over the Bering Strait which brought Asians to North America in prehistoric times.
It doesn’t seem feasible that a genome wound inside a human cell could reveal one iota about human foot traffic. Yet, it already has. Using the human genome as their magnifying glass, population geneticists are sleuthing our roots as humans. They begin by gathering their clues from a living, indigenous population — one that hasn’t budged from its original homeland for thousands of years. That population also has to be homogenous, sharing the same idiosyncratic gene mutations. After the population geneticists swab their cheeks, and analyze their genome, they can search for the descendants of the first group of defectors to pack their bags, pick up and move.
The group that moved to new land then developed their own new set of mutations, or errors in gene replication, now no longer shared with their former home base. Out of the 3.2 million base pairs of every new baby’s genome, there will be lots of mutations — the generally accepted number is 100 mutations, although some recent research has instigated a debate among geneticists. Regardless, because each generation has its own unique combination of mutations from its own individuals, they can serve as markers or “breadcrumbs,” as Dr. Spencer Wells, National Geographic’s Genographic Project Director, calls them, for geneticists to follow geographically and temporally.
Swabbing the cheeks of indigenous populations allows theoretical population geneticists to trace groups of people by following their mutations. “You can actually theoretically trace the markers all the way back to one person would have that set of mutations,” Dr. Brenna Henn, an anthropological geneticist and professor at Stonybrook University Department of Ecology and Evolution, told the International Science Times. Henn had offered her 50 undergraduates the opportunity to go for the swab. About 12 of her students took them up on the offer, some of whom will be discussing their results with rest of the class.
By volunteering, the students were spared the $200 testing fee, most of which is funneled back to the project. (Anyone who wants to spring for the ancestry kit can do so at www.genographic.com.) On April 23, the students will return to the museum for a summary of results with a panel of prominent population geneticists including Henry Louis Gates, Jr.
Student volunteers were both on academic and personal missions. “Being a bio major, I was really interested in seeing what this has to offer,” Thomas Aponte Hurt, 25, of Harlem, and a senior at City College, told the International Science Times. “It’s part of my anthro-genomics class requirement,” he said, “but I’m doing this for my own personal insight and understanding of my lineage. I guess I’m looking forward to seeing how far removed my ancestors are from Africa. I would just kind of like to know more of where I come from, because it would help me understand who I am and help me bridge the past and the future.” Hurt is also intrigued by the presence of his Caucasian paternal great great-grandfather. “I’m kind of interested in understanding that lineage,” he said. Hurt, whose anthro-genomics class contains “lots of ethnicities and nationalities,” is looking forward to comparing results with his class members. “It’s going to be real cool see how closely related we are to our classmates. I may have a couple of different cousins in my class,” he said.
Dannah Rae Sajorda, 22, of Manhattan, a biology major at Stonybrook University and a student of Dr. Henn, told the International Science Times she volunteered for the Genographic Project “both because my personal interest coincides with my academic major, and I want to do something with genetics later in life.” But Sajorda, born in the Philippines, emphasized she hopes unravelling her genetic code will help her understand her personal history. “The Philippines is such a diverse country,” she said. “I noticed my cousins and I all look pretty different, with all different skin colors and eye shapes. Some of my relatives look more Spanish, some native, and some have more Asian features. It’s really interesting. I don’t really know what to expect at all.”
Genographic Project results are posted anonymously online, allowing the students to chat (if they know the language) anonymously with the other 650,000 people in 130 countries who have already given their spit. But the results are not fool-proof, Henn said. For one, a new consensus about the the average number of mutations per baby would sigificantly throw off the reliability of genome mapping that was calibrated on the notion of 100 markers per baby. “If it turns out that many more mutations occur per generation than we thought, how we track the differences between different populations would have to be revised,” Henn said.
The genetic material from the student’s swabs gets analyzed by a technology called SNP (single nucleotide polymorphism), which has arrays on computer chips probing for 150 thousand different mutations. But it’s not fail-safe, Henn says. “Although it’s a well-established technology, there are certain biases associated with it,” she said. The computer scanner analyzing people’s genome is calibrated to look for only for certain mutations, and not others. Right now, a Native American would be identified as an Asian, as there is no scan for Native American markers after they hit the North American continent. “If you didn’t have any Native American on the chip,” Henn said, “their profile would look East Asian.”
A similar so-called “ascertainment bias” significantly blurs the genetic picture from Africa. So far, the Genographic Project has only been able to test the Yoruba people in Southwest Nigeria and Benin — which means the SNP is only calibrated to seek their mutations, and not for those of other African peoples. If Hurt’s forbearers were not Yoruba, his geneology would hit a brick wall. “What if his ancestry comes from Central African Rainforest?” Henn wondered. “What about all the mutations that are not on that chip? How does analyzing a subset of mutations that are present in the population skew your view of the true pattern of genetic diversity?”
Dr. Wells acknowledged that there is ascertainment bias built into the Genographic Project’s markers. “We don’t split it out according to tribe,” Wells told the International Science Times, “We’re not reporting on tribal affiliation, because we don’t have extensive samples from all over Africa. At this point, we’re still in the process of collecting data.
We’re trying to sample more, and as we collect data from more people, we can put their data in our reference data base.”
But it’s remarkable what the students will be able to glean from their DNA: They’ll be able to find out what percent Neanderthal they are. Students whose ancestors hail from the sub-Saharan African will be carrying less than one-tenth to one-half of one percent of Neanderthal genome, said Wells, while most non-Africans will see two to 2 1/2 percent Neanderthal in their DNA. People whose ancestors hail from Eurasia will see up to four percent Neanderthal in their genetic material. Wells told the International Science Times that students who discover they have more Neanderthal in them than they were counting on should be nonplussed. “I don’t think how much Neanderthal you have in you says if you’re more or less primitive,” he said. “It’s just part of the human genome.”
Originally published by International Science Times