Science Has Just Made Jurassic Park Impossible

If you’ve ever wondered whether Jurassic Park can ever become a reality, rest assured: it can’t. According to a new study, the half-life of DNA is less than a thousand years old, so finding a perfectly preserved DNA sample that’s millions of years old is, by probabilistic measures, quite negligible.

Palaeogeneticists led by Morten Allentoft at the University of Copenhagen and Michael Bunce at Murdoch University in Perth, Australia, examined 158 DNA-containing leg bones belonging to three species of extinct giant birds called moa. The bones, which were between 600 and 8,000 years old, had been recovered from three sites within 5 kilometres of each other, with nearly identical preservation conditions including a temperature of 13.1 ºC. The findings are published in Proceedings of the Royal Society B.

By comparing the specimens’ ages and degrees of DNA degradation, the researchers calculated that DNA has a half-life of 521 years. That means that after 521 years, half of the bonds between nucleotides in the backbone of a sample would have broken; after another 521 years half of the remaining bonds would have gone; and so on.

You can read more here.

On Wrongful Convictions and DNA Evidence

DNA analysis has helped exonerate dozens of people who had confessed to violent crimes. But against Juan Rivera, as detailed in this New York Times piece, prosecutors used new and novel theories to explain away the scientific evidence. How did they do that?

Some interesting facts about DNA evidence:

In the years before DNA evidence was introduced to the legal system, little was known about the extent of wrongful convictions and the situations in which they occurred. That changed in 1986, when an English scientist used DNA testing to help exonerate a man accused of raping and killing two teenage girls (the evidence also led the police to the real killer). Since then, DNA testing has helped exonerate 280 convicted felons in the United States and has exposed deep flaws in our legal system, including misconduct by the police and prosecutors and egregious mistakes made by witnesses and forensic scientists. In his 2011 book, “Convicting the Innocent,” Brandon Garrett, a law professor at the University of Virginia, examined most of the case files for the first 250 DNA exonerations. Garrett found that 76 percent of wrongly convicted prisoners were misidentified by a witness and half the cases involved flawed forensic evidence. The testimony of an informant, often a jailhouse cellmate of the accused, was pivotal in 21 percent of the cases. Perhaps most surprising, 16 percent — virtually all of whom were subjected to interrogations lasting several hours and, in many cases, days — confessed to crimes they didn’t commit. Garrett pointed out another, striking detail in the false confessions: in 38 of 40 false confessions, the authorities said defendants provided details that could be known only by the actual criminal or the investigators, thus corroborating their own admissions of guilt by revealing secret information about the crime that could only have been provided by them.