DNA analysis reveals there are four distinct giraffe species, not one • Hacker News Board

Re: DNA analysis reveals there are four distinct giraffe species, not one

#91

Post by Dylan16807 » Fri, Sep 09, 2016, 10:44 PM UTC

MustardTiger wrote: post #85

Dylan16807 wrote: post #67

Earlier quoted context omitted.

>The average proportion of nucleotide differences between a randomly chosen pair of humans (i.e., average nucleotide diversity, or pi) is consistently estimated to lie between 1 in 1,000 and 1 in 1,500 (refs. 9,10). This proportion is low compared with those of many other species, from fruit flies to chimpanzees11, 12, reflecting the recent origin of our species from a small founding population13. >In other words, ap…

>I'm not sure how this supports your point Why not? What subspecies has more than 10% of the species wide variation? I can't find any. This is what I meant. Just to report facts you have to try to couch it in politically correct disinfo. "This will make it sound like races aren't real, even though the data clearly shows they are". Just like "we're 99.8% the same DNA!". Yeah, but most of that DNA is also the same as a…

> What subspecies has more than 10% of the species wide variation?

So you're not saying that the racial differences are large in absolute terms of how many genes are different, you're saying that they're large relative to the low overall genetic diversity of humans? That might be true[1], but that's because the denominator for a relatively new species is small, not because the numerator is large.

Also to me, a layman, if only 10% of our intra-species genetic diversity is between races that sounds like a pretty good case for disregarding race in the vast majority of situations.

> I said subspecies.

You said "The genetic distance between human races is greater than many species, and virtually all subspecies".

[1] What are the numbers for canis lupus, giraffes, etc. so I can compare?

Re: DNA analysis reveals there are four distinct giraffe species, not one

#92

Post by rcthompson » Fri, Sep 09, 2016, 11:09 PM UTC

benkuykendall wrote: post #88

sndean wrote: post #73

I'm pretty happy with a (the?) species definition in microbiology: It's a little more complicated than that, and some important people (especially in the older generation) don't like it, but it's a good / quick standard. [0] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1764935/

Presumably a "species" should be an equivalence class, right? So the relation "A and B are of the same species" should be transitive, symmetric, and reflexive. Symmetry is easy (an organism shares 100% of its genome with itself) as is reflexivity (A shares n% with B iff B shares n% with A). However, transitivity does not follow obviously: for example, A and B could share 98%, B and C could share 98%, but A and C coul…

Unfortunately, speciation is mostly a continuous process, so there's no way to define species by some kind of "degree of similarity/dissimilarity" metric and have it be a transitive relationship. Any species definition that is completely transitive will necessarily have edge cases where two extremely similar organisms fall on different sides of an arbitrary threshold and are declared to belong to two different species.

The classic example of non-transitive species relationships from sexually reproducing organisms is a "ring species": https://en.wikipedia.org/wiki/Ring_species

Re: DNA analysis reveals there are four distinct giraffe species, not one

#93

Post by rcthompson » Fri, Sep 09, 2016, 11:19 PM UTC

kristofferR wrote: post #64

sandworm101 wrote: post #37

Earlier quoted context omitted.

They were believed to be sub-species and so I doubt zoos mixed and matched. The real outcome seems to be that the species is now 1/4 its previous size. Where there was once one endangered species, now stand four very endangered species. Similar and more dramatic story with mantas: http://news.nationalgeographic.com/news/2008/07/080731-new-r...

There's a philosophical question in the fact that something just became more treasured because of DNA testing results, but I'm not even going to attempt answering that.

There's no need to invoke philosophy here. It's pretty well accepted that an ecosystem with less biodiversity is more fragile, and from that perspective the extinction of a species is a concerning event, particularly if the extinction was accelerated by human actions. If new information indicates that a species or group of species is in much greater danger of going extinct than was previously thought, then it makes sense to prioritize conservation efforts for those species more highly.

Re: DNA analysis reveals there are four distinct giraffe species, not one

#94

Post by wodenokoto » Sat, Sep 10, 2016, 6:56 AM UTC

guessmyname wrote: post #36

wodenokoto wrote: post #26

Earlier quoted context omitted.

they work for me

How? Every time I scroll down to click one of the links the website scrolls my browser back up and loads a new article below the one I was reading. I don't want to read more articles, I want to click the links at the bottom of the website!!! I was not asking if the links work, they probably do, I am asking how do I "click them" if the website keeps moving the webview back up when I scroll to the bottom?