Beth Shapiro Answers
First, can we create Jurassic Park? From the perspective of a scientist working on ancient DNA, the answer is definitely no. Theoretical predictions based on the biochemistry of DNA predict that DNA fragments will only survive in ancient remains for around 100,000 years. But this doesn’t mean whole chromosomes, or even whole genes, but tiny, often highly damaged fragments of DNA. And even this is only in the best environments, such as very cold, very dry, and/or salty places. Most of our research depends on being able to find exceptionally well-preserved specimens, which means they must either be very young, or slightly older but from cold and dry places. In my own research, my collaborators and I focus on regions like the arctic permafrost of Siberia, Alaska, and the Yukon Territory. In those places we can find bones from animals that lived during the last Ice Age, such as mammoths, stilt-legged horses, steppe bison, short-faced bears, North American lions… and the list goes on. We then try to extract DNA sequences from the bones of these creatures or from the soil around the bones to learn something about what the environment was like at that time. We ask questions like: How big were the populations of the different species? Why did some species go extinct when others did not? How important was climate change, or human hunting, in the extinction of so many large mammals?
So, Jurassic Park is certainly out of the question. But what about Pleistocene Park? Well, I haven’t actually brought up all of the problems that ancient DNA research runs into. Because DNA starts breaking down immediately after the organism dies, the DNA fragments we can recover from these “ancient” bones and soils are not in good shape. The strands of DNA are damaged, broken, and balled up in ways that stop our lab techniques from working. In fact, ancient DNA studies normally rely on a particular type of DNA: mitochondrial DNA. The mitochondrial genome is separate from the nuclear genome, which is where most of the genes that make mammoths look like mammoths, for example, would be. Because there are many more copies of the mitochondrial genome than the nuclear genome in every cell, it is more likely that these fragments will survive in large enough quantities to be amplified. So, we don’t have very much information about the genes that make a mammoth different from an elephant, or those that make a North American lion something other than African lions. And even the mitochondrial DNA fragments that we can get out of these remains are small: normally around 100-200 bases long per fragment, whereas the entire human genome is more than 3 billion bases long. To cut the explanation short—we would need enormous technical breakthroughs to be able to recreate a mammoth or North American lion. We would need better techniques for extracting and amplifying DNA that would allow us to get both mitochondrial and nuclear DNA. We would need to be able to piece together the tiny fragments of DNA that we can amplify from ancient remains. We would need a way to line these up, package them into chromosomes, and package those chromosomes up into useful genetic material. Then we would need to find a host, work out the developmental differences and the list (again) goes on. We’re really not there. At least not yet.
Which brings me to the second part of my question, which in my mind is more important. Should we bring back extinct species, if there ever comes a point when we actually can? Is this the use of our financial and intellectual resources, or would it be a better bet to concentrate on, for example. conserving species and habitats that are currently under threat of extinction? What do you think?
