I began thinking about this post when I read a National Geographic article about the possibility of cloning a woolly mammoth. (The print version of the magazine is always good reading, & the on-line version has heaps of extra stuff.) But, just because this now seems to be on the verge of being possible, does that mean we should actually do it?
In itself, cloning isn't really new. In fact, a form of cloning has probably been practised ever since the first orchardists began propagating plants by taking cuttings (and when you think about it, the process has been going on in nature for billions of years, every time an organism reproduces asexually). And identical twins or triplets are effectively clones as well: cloning is the production of an individual that is genetically identical to another. It's possible to clone genes, too, by inserting a gene into a bacterial plasmid; because plasmids replicate independently of the bacterium itself, this technique quickly yields multiple copies of that gene. Here's a link to a nice animated tutorial on the subject.
But I think cloning first really made it into public consciousness in a big way when Ian Wilmut's team cloned 'Dolly' the sheep, back in 1997. Scientists had cloned animals before, beginning with frogs in the 1970s, but Dolly seemed different because she was a mammal. In people's imaginations, this opened the door to the possibility of cloning humans.
I remember talking about this with students at the time. They were excited by the idea that, if my child or husband died - of disease or accident - I'd be able to bring them back by cloning. This seemed a bit pointless to me at the time, & it still does. Say it was my husband. He's 50+ now. If he did die & I was in a position to have a clone produced, it would be a jolly long wait before he got to the age where he'd be interesting - & by then I'd be too old to be interested, anyway! And besides, it wouldn't really be him - he'd be brought up in a different time, in a different way, by different people, & all those experiences shape an individual's personality. Not to mention any influence that the 'host' cell might have - remember, the only way we have at present to clone a mammal is to insert a nucleus into an enucleated egg cell. But that egg cell has its own mitochondria, & these can have subtle influences on what goes on as the embryo forms & grows.
Anyway, Dolly was produced by a process called somatic cell nuclear transfer. The nucleus of a mature body cell (a somatic cell ie not a sperm or egg) is removed from that cell & transferred into an egg cell that's had its own nucleus removed. This 'hybrid' egg cell is then treated electrically to fuse cell & nucleus, and initiate cell division & embryo formation, after which the embryo is implanted into the uterus of a host mother. The process isn't easy - it goes through a lot of eggs for the production of a single viable embryo - but it is certainly do-able & has been used to produce clones of many different mammal species. So I guess it's understandable that attention should move from cloning living organisms to bringing extinct ones back to life - not a novel idea at all, for a generation brought up on Jurassic Park.
And cloning a mammoth should be a much more achievable task than taking on a dinosaur. For one thing, they became extinct only relatively recently, with the waning of the last 'ice age'. And because many mammoths have been frozen, preserved in the permafrost of the Arctic tundra, there's the potential to extract usable amounts of DNA from their corpses. Indeed, about 70% of 'the' mammoth genome has so far been sequenced. Mind you, that's not one complete length but bits & pieces, so one of the tasks facing would-be mammoth cloners is going to be sorting it all out into chromosomes (problematic when you don't know how many chromosomes mammoths actually had), working out what's missing, & coming up with a way to fill in the gaps. Then you have to package your chromosomes into an artificial nucleus, fuse this with a host egg, & implant the resultant embryo into a surrogate mother - an Asian or Indian elephant. But scientists say it's theoretically possible nonetheless.
But - just because we can do this, should we? Any mammoth produced by this technique would be at best a curiosity, a lonely individual in some sort of zoo, its original ecosystem long gone. There might be satisfaction in overcoming all these challenges, and kudos to be gained for completing the task successfully. But really, ethically, is it the 'right' thing to do?