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

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

#31

Post by Retric »

adekok wrote: post #28
Retric wrote: post #5

Earlier quoted context omitted.

Humans have not really had enough time as independent populations to diverge much. The north american land bridge disappeared ~14,500 years ago so only ~14,000 years as separate populations. African > Eurasia had regular exchanges as they where within relatively short walking distances.

> ~14,000 years as separate populations. Perhaps even less. http://www.andrewcollins.com/page/articles/romanbust.htm There was at least some contact between North America and Europe, close to 2K years ago.

The baring strait is also only 51 miles so there was likely quite a bit of accidental crossings if nothing else. For comparison Australia was populated around 65,000 to 75,000 years ago and that takes more than 200 miles by sea.

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

#32

Post by seanc »

dschiptsov wrote: post #27

The classic operational definition of different species, as far as I remember, is that cross-breading between species is not possible.

My understanding was that they might be able to crossbreed, but offspring are not fertile, e.g. hybrids such as mules and ligers.

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

#33

Post by dogma1138 »

Retric wrote: post #10
dogma1138 wrote: post #7

Earlier quoted context omitted.

That's not true we've seen speciation happening in front of our eyes with some species. While time is a factor 14,000 is more than enough for humans to speciate, the reason why this hasn't happened to humans is something that is actually a subject of research today.

Humans have a long reproductive cycle, so that's under 1,000 generations. For comparison bacteria can reach 1,000 generations in ideal conditions in less than 1 year.

We've had documented cases of speciation of various types of animals within only a few generations, birds for example tend to do that rather quickly as well as rapidly form ring species.

And this isn't because birds are special but because they tend to migrate, in other cases natural or manmade barriers that split a species into distinct groups have also causes speciation after only a handful of generations. Besides birds where it's common due to migration patterns "man caused" rapid speciation has also been observed in rodents (squirrels/mice) and various types of fish.

http://evolution.berkeley.edu/evolibrary/news/100201_speciat...

You do not need a 1000 generations to speciate.

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

#34

Post by alexbock »

dschiptsov wrote: post #27

The classic operational definition of different species, as far as I remember, is that cross-breading between species is not possible.

Two individuals may be capable of breeding and reliably producing fertile offspring but still be considered different species if they would never mate "naturally". This may be due to geography, different mating seasons, different songs or appearances, etc.

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

#35

Post by micahbright »

achr2 wrote: post #30
dschiptsov wrote: post #27

The classic operational definition of different species, as far as I remember, is that cross-breading between species is not possible.

It's a very blurred line.

It's really just a social construct.

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

#36

Post by guessmyname »

wodenokoto wrote: post #26
guessmyname wrote: post #20

Off topic — How do I click the links at the bottom of this website? EDIT: To clarify, as some people thought this was a stupid question... 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 pro…

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?

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

#37

Post by sandworm101 »

kristofferR wrote: post #17

Since this wasn't known before, am I right to assume that a lot of giraffes in zoos are hybrids of the different species?

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...

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

#38

Post by MustardTiger »

Retric wrote: post #24
dalke wrote: post #18

Earlier quoted context omitted.

They are "generally classified as separate species", says https://en.wikipedia.org/wiki/Polar_bear#Taxonomy_and_evolut... : > A comparison of the nuclear genome of polar bears with that of brown bears revealed a different pattern, the two forming genetically distinct clades that diverged approximately 603,000 years ago,[25] although the latest research is based on analysis of the complete genomes (rather than just th…

Most brown bears have about 2 percent genetic material from polar bears, but one population, the ABC Islands bears has between 5 percent and 10 percent polar bear genes, indicating more frequent and recent mating. Ed: I don't disagree with what you're saying, I just don't think it's relevant to discussions of DNA. We can call Pluto a potato, does not change anything. As to classification the trend is clearly to call…

What you quoted supports his rebuttal, not your claim. You are completely backwards, the trend is away from that. The myth that interbreeding makes them the same species was never accurate, but it is completely unused in modern times. For example, the very article that started this discussion saying that giraffes are 4 species not one. We classify them as such based on DNA evidence. The fact that all 4 species can produce fertile offspring when cross breeding is not relevant at all.

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

#39

Post by nitrogen »

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?

Are you talking about the linked site? HN cerainly doesn't do that.

As for infinite scrolling, I am definitely not a fan myself, and this is an example of why.

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