cowbirdy t1_iwbhtjp wrote on November 14, 2022 at 12:21 PM

Reply to comment by deadmeatsandwich in How do we have more woolly mammoth DNA than dodo DNA if woolly mammoths died off thousands of years ago and dodos only died off a few hundred? by Memer9456

This is true of old bird study skins which often used arsenic to prevent bugs from eating them, but modern study skins don't use any harsh chemicals in the preservation process - just cotton and sunlight. Sometimes dawn dish soap will be used if the skin is particularly dirty.

Also even historical bird skins don't tend to have large amounts of arsenic on the foot pads which is where DNA is often sampled from due to its thickness and its remarkably successful compared to other taxa. Though the addition of arsenic does inhibit PCR success,its not found at a particularly high volume on the feet of historical study skins.

Here's a link to one reference, but I'm also just speaking from experience preparing study skins and picking up info from there.

This isn't to contradict the fact that there is less dodo DNA than mammoth - but preserved bird skins are some of the easiest to extract DNA from, compared to ethanol preserved specimens (common for herps and insects) and mammalian taxidermy.

I think your point from another comment about how mammoths were essentially frozen is the primary reason that there is more usable DNA.

lookmeat t1_iwcr0ks wrote on November 14, 2022 at 6:02 PM

Yup, the thing is, even with preserved you still have to contend with the natural decay of DNA. It's a half life of 521 years. This doesn't mean half the DNA is gone, but half the bonds. So after a couple centuries all you'd see are a bunch of pieces of DNA that you have to, somehow, assemble in the right order, that's a puzzle on a different level. The only way to slow down there process is to freeze which, Uber right conditions, can extend the half life by thousands of years.

Also wooly mammoths are not that old. The pyramids where built when there where still mammoths. But that depends what mammoth we are talking about.

And that's the other reason. When we talk about mammoths, we are talking about many species, that lived across all the north of America and Eurasia for around 5 million years. When we talk about dodos, it's a species that only lived in an island (not Madagascar but way smaller Mauritius) over who knows how long (their branch splits 25 million years ago, but they are so different from their closest relative species that it's hard to define when the actual dodo, vs predecessor species, evolves) but it may not be that much. So the chances that you have pieces of dodos that happened to be in a place that preserve them well enough is much lower than that of any mammoths'.