Human Genome Project surpasses expectations by creating 2,500 sequenced genomes
﻿Eight ﻿years ago, Goncalo Abecasis explained to a group of scientists that he would sequence 1,000 genomes from people all over the globe, thus﻿ began the Human Genome Project. Now with the project coming to a conclusion, it has sequenced more than 2,500 human genomes from 26 separate groups of people all around the world. This research has provided a pathway to thinking about more than just humans, but humanity.

When the geneticist Gonçalo Abecasis stood up in front of a group of scientists in 2007 and proposed sequencing 1,000 genomes from people all over the world, he had no idea how he was going to pull it off. The Human Genome Project had published the first complete map of the human genome just four years earlier, and the technology remained exorbitantly expensive. “Imagine you’ve done ten of these,” Abecasis says today of the number of human genomes that had been sequenced at the time. “The first one cost $3 billion, and the other ones cost several million. And you say, ‘what if we set out to do a thousand?’”

The price wasn’t the only hurdle. “When we first started talking about doing these genome-wide comparisons between populations”—i.e., groups of people from different continents or with different ancestries—“there was a lot of tension,” remembers Abecasis, now at the University of Michigan. That’s because, frankly, “human population” sounds a lot like “race.”

Sequencing the human genome showed that humans are all much more alike than different; genome pioneer J. Craig Venter told the International Herald Tribune that the Human Genome Project proved once and for all that “the concept of race has no scientific basis.” And here was Abecasis, proposing that the next big international genomics project target precisely those differences and figure out what they mean. “There was some trepidation,” he says.

Now, eight years later, Abecasis’s idea—dubbed the 1000 Genomes Project—is coming to an end. They exceeded their goal, having sequenced over 2500 human genomes from 26 distinct groups of people around the world. (The collaboration’s last two papers are in Nature today.) Sequencing technology has improved by leaps and bounds since 1000 Genomes began, and the price for a whole genome sequence has fallen to a few thousand dollars. At least in the scientific community, trepidation about studying the genetic differences between groups of people has largely disappeared. In fact, many consider it the most important work they could possibly do. As the University of California, San Francisco sociologist Catherine Bliss puts it in her book Race Decoded, genomics has gone from being a “race-free” science to being a “race-positive” one.

To understand why, you have to understand what genetic variation is and what it does. Everyone’s genome is slightly different from everyone’s else’s, unless you’re an identical twin or, um, a clone. You inherited some of the differences from one or both of your parents; others might be random copying errors made when your genome was being pieced together. In their final 1000 Genomes paper, Abecasis and his colleagues estimate that a typical genome differs from the human reference genome---about 3 billion base pairs in all---in 4.1 million to 5 million places. It’s just a handful, really. But it's enough to make a difference.

Now, what happens if a relatively small group of people, with all their genetic quirks, gets separated from other populations? They’ll pass down those quirks to their children, and they’ll pass them along again, and so on. Eventually, those particular variations become more and more common in that isolated population, even though they might remain rare in the global population as a whole.