The 2009 TIME 100

Until recently, our only means of understanding evolution were looking at living species and examining the fossil record. Over the past 15 years, the ability to sequence and analyze DNA has given us a new and clearer understanding of evolutionary events — but even with these advances, we've been limited. Getting the genetic code of species that have become extinct — including some of the ones we most want to know about — has been largely impossible. That's all starting to change, however, thanks to the work of people like biologists Stephan Schuster and Webb Miller.

Last year, Schuster, 47, and Miller, 65, both of Penn State University, successfully sequenced the DNA of the 20,000-year-old woolly mammoth. In doing so, they helped science overcome what had been seen as an insurmountable obstacle. Most biologists and geneticists thought that nuclear DNA, the genetic material contained in the nucleus of a cell, degraded rapidly after death and would not be available for analysis.

Schuster and Miller found they could isolate partly degraded DNA from the shafts of preserved mammoth hair after bleaching the hair to remove any traces of bacterial DNA. This exciting finding could allow scientists to unlock the secrets of thousands of ancient species preserved in museums. It also offers the tantalizing possibility of sequencing the genomes of historical figures from just a lock of hair.

Many have speculated that the next step from the important work of Schuster, Miller and others will be to resurrect extinct species. This has actually been done, but only with the tiny and lethal 1918 influenza virus. Using new synthetic genomics tools and techniques, the virus was regenerated from RNA isolated from a flu victim buried in permafrost. However, this was possible only because the flu's genome sequence was 100% accurate and complete.

Given the current quality and incompleteness of the woolly-mammoth genome sequence, it is unlikely that we will see mammoths walking the earth again. Still, Schuster and Miller's pioneering work will undoubtedly inspire many to push the limits of DNA analysis, both to explore our past and perhaps predict our future.

Venter successfully mapped the human genome in 2001; he sequenced his own genome in 2007

Fast Fact: Hair samples from 10 mammoths were needed to build one whole genome

View the full list for "The 2009 TIME 100"