Why do they clone cats and dogs instead of extinct species?

Factual Questions
1

Like that river dolphin that just vanished in China. I bet a couple of the country’s leading biologists have preserved samples.

Or pandas. Why fuss over making them mate. Is there a lack of test tubes and surrogate animal mothers?

2

Relative availability of sperm & eggs? It’s not like they hack off a toe and toss it into a petri dish, after all.

3

Even if you have a DNA sample, you still need to fertilize an egg and gestate the fetus somehow.

4

You don’t use sperm to clone. And you don’t need eggs either. You could take skin cells (or other cells) from the endangered species and use the egg of a closely related species (if one exists), then use that species as a surrogate. But it’s expensive and not very easy to clone even cats and dogs. Success rates are something like a few percent, so you try hundreds of times just just to ensure that you’ll get a few successes. This was done with the Gaur, an although the cloned animal died, it wasn’t due to the cloning itself (or so we think).

But in order to produce a viable, wild population, you’d have to do this dozens or hundreds of times. Cloning one or two would do no good-- you’d be right back where we are now in a few years.

5

Well, there are probably a few reasons. Ones I can think of:

  1. No complete set of DNA from the extinct species (so rules out anything that didn’t go extinct in the last decade or so).

  2. Even with a complete DNA sample, you still need a compatible mother. There’s a lot more interaction between a fetus and a mother than passing oxygen and carbon dioxide back and forth. And we have no idea what kind of nutrition, antibody compatibility, and physical space that a random extinct animal needs. Even cloning into a host from very closely related species is tricky, let alone trying to find a host for a T. Rex.

  3. Opal might not give her permission.

  4. With currently existing, but very threatened species, the goal is not only to have more individuals, but to try and increase genetic diversity. If we produced 10,000 cloned california condors, the species still wouldn’t be in much better shape (especially after the same virus kills all 10,000 kooky kloned kondors).

  5. We’re still learning how to do cloning. Sheep and a few other animals is all we know how to do right now.

6

OK, once you have achieved a viable blastocyst from the cloned cell, what do you do with it? Except monotremes, mammals have this odd reproductive habit of viviparousness. That blastocyst needs a womb around it, an amnion suspending it, and a placenta nourishing it. And it needs to be the same or a closely related species to avoid spontaneous abortion or fetal death, at least as I understand the obstacles.

There is an outside chance one could clone a mammoth and use a cow elephant as host mother – there are intact frozen cells to clone, and while elephants are in a different genus, they are very closely related genera. (It’s possible Elephas is one of those highly variable species, like Equus and Canis, and mammoths are actually species of Elephas.

But having done that, where do you raise it? The beiji dolphin is adapted for life in the Yangtse; is there a river somewhere they could be introduced into safely and with a good chance of survival? Not an easy question to answer.

7

I wouldn’t even say we know how to do sheep. They only produced one viable clone out of several hundred attempts, and that one aged prematurely.