Ancient DNAโค Research Faces Reality Check: Limits โคto Recovering Cretaceous-Era Genetic material
Recent attemptsโข to extract DNA from โขfossils โคdating back to โthe Cretaceous Period-betweenโ 145 and 66 millionโข years ago-have โyielded genetic material not fromโค dinosaurs or their contemporaries, but โfrom much younger bacteria. This discovery underscores the fundamental โlimitations of DNA preservation and dashes hopes of readily unlocking the geneticโค secrets of lifeโข from deep time.
While โthe popular creativity,โฃ fueled by fictionโข like Jurassic Park, envisions retrieving intact DNA from ancient organisms, โscientific โresearch reveals a far moreโข constrained timelineโ for genetic survival. A 2012 study, co-authored by paleogeneticist Michael Gilbert, modeled the decayโค rate of DNA, finding its “half-life”-the time it โtakes for half of the DNA bonds to break-is approximately โ521 years. This means even under ideal conditions, complete โฃDNA degradation is certain overโฃ geological timescales.
Gilbert’sโ team analyzedโ mitochondrial โDNA from 158โ bones ofโฃ extinct moa birds in New Zealand, previously dated โขusing carbon datingโค methods, to determine this decay rate. Their model predicts a maximum survival of around 6.8 million years for DNA, โfar short ofโ the tens โof millions of years required for Cretaceous-era recovery.
“The best conditions forโ preserving ancient DNA are cool, dark,โค dry, and relatively โขrecent,” explains Jennifer Raff, a biological anthropologist at the University ofโ Kansas. “Permafrost is โusually the โขbest place to find well-preserved DNA.” โฃThe โคbacterial โขDNA recently found in Cretaceous fossils likely โoriginated from more recent contamination, โhighlighting the challenges of โdistinguishing ancient genetic material from modern intrusions.
This research clarifies the boundaries ofโ ancient DNA analysis, focusing future โefforts on more recent fossils and refining techniques to minimize contamination and accurately interpret โคfragmented โgenetic data.