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

#41

Post by empath75 » Fri, Sep 09, 2016, 3:25 PM UTC

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.

Man that's a pretty strong statement to make based on a tiny sculpture that looks vaguely roman.

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

#42

Post by clort » Fri, Sep 09, 2016, 4:07 PM UTC

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…

noscript solves it for this site at least, since the script which does it appears to live on rgstatic.net

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

#43

Post by dalke » Fri, Sep 09, 2016, 4:09 PM UTC

dogma1138 wrote: post #33

Retric wrote: post #10

Earlier quoted context omitted.

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…

The first description in what you pointed to says "could signify the beginning of a speciation event". It doesn't say the result is a new species.

The second description concerns a pairing between two hybrids which started a new lineage. It uses the term "lineage" instead of saying there is a new species.

> These two examples make it clear that the division between species is not a black-and-white issue. Rather, speciation occurs as many different sorts of traits (physical, behavioral, and genetic) diverge from one another along a continuum. Because of this, biologists sometimes disagree about where to draw the line between incipient species — about when a division has become deep enough to warrant a new species name. Whatever we choose to call them, these two cases clearly illustrate how a lineage can split and begin to make its way down two separate evolutionary paths.

Regarding ring species, https://en.wikipedia.org/wiki/Ring_species says "Currently, there are four known forms of life that appear to match the definition of a ring species". Frankly, I thought there were more. It would suggest that birds don't tend to rapidly form ring species.

> You do not need a 1000 generations to speciate.

Are either of those two cases described in the literature as a new species, or are they given as a subspecies, or variant, or fertile hybrid, or some other term?

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

#44

Post by Myrmornis » Fri, Sep 09, 2016, 4:11 PM UTC

kristofferR wrote: post #19

bcraven wrote: post #8

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Species_problem The word "Species" is mixed up in all manner of biological and sociological turmoil. I was even of the impression that becuase of DNA sequencing the term is falling out of favour amongst researchers.

Would DNA sequencing just make it easier to distinguish different species (like in this case) from each other instead of making the term more problematic?

The problem is more the definition of the term, rather than availability of adequate data. A lot of biologists (and humans!) grew up thinking that "species" had a clear and obvious definition. One result is that their views are very entrenched and people don't realize that there's even a serious definitional problem at hand affecting a critical area of biology.

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

#45

Post by dogma1138 » Fri, Sep 09, 2016, 4:12 PM UTC

dalke wrote: post #43

dogma1138 wrote: post #33

Earlier quoted context omitted.

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…

The first description in what you pointed to says "could signify the beginning of a speciation event". It doesn't say the result is a new species. The second description concerns a pairing between two hybrids which started a new lineage. It uses the term "lineage" instead of saying there is a new species. > These two examples make it clear that the division between species is not a black-and-white issue. Rather, spec…

Yes they are a species, i think you are working on a different definition of a species than the accepted common one.

Also don't rely on wikipedia for accurate information about many subjects, it's ok but it's far from perfect or being technically correct.

As for the rest of your argument that's semantics and it clearly misses the conclusion of that article:

"While we can't know the fates of these lineages, directly observing such divergences in real time highlights the fact that we don't always need to look into the distant past or far off future to find examples of speciation in action. Evolution is occurring all around us. We just need to learn where and how to look for it."

We have examples of speciation and divergence in real time over a handful of generations, a species at the end is a group which is capable and practices interbreeding amongst its members but does not breed with others.

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

#46

Post by Retric » Fri, Sep 09, 2016, 4:24 PM UTC

MustardTiger wrote: post #38

Retric wrote: post #24

Earlier quoted context omitted.

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 pr…

The long term definition was more or less 'A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.' This brings up the arguably semantic idea that physical separation is enough even if they are still genetically compatible.

So, in theory you can have genetically compatible separate species as soon as they are no longer capable of interbreeding. However, as Humans and Brown bares are both biologically capable of interbreeding and live in such a manner that the do interbreed they don't fit that definition. Temporary barriers are not necessarily enough as they may exchange DNA in the future.

PS: Ring species are considered a single species because a mutation can start at one end and given time make it's way around the ring. Thus they are a single pool that can and will exchange DNA.

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

#47

Post by openasocket » Fri, Sep 09, 2016, 4:25 PM UTC

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.

If only it was! But then we discovered "ring species" (https://en.wikipedia.org/wiki/Ring_species) which threw a monkey wrench into what was once a simple definition. Basically, there are populations of animals A, B and C, where A and B can inter-breed, B and C can inter-breed, but A and C can't. So our definition of species no longer satisfies the transitive property, and it all falls apart. As far as I know, this issue hasn't yet been satisfactorily answered in the case of ring species.

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

#48

Post by DougWebb » Fri, Sep 09, 2016, 4:26 PM UTC

dalke wrote: post #25

MustardTiger wrote: post #16

Earlier quoted context omitted.

>The paper is about species, not subspecies. And my reply is about subspecies, and our refusal to apply the same standards we apply to other animals to ourselves. I do not understand your confusion. >Humans do not meet the phylogenetic criteria which justifies the use of "subspecies" We have greater genetic difference between races than ANY example of subspecies in existence. I am very aware that a large group of peo…

Yes, my complaint is that you are highjacking an article on species differentiation in giraffes to talk about purported human subspecies. No, we emphatically do not have that high of a genetic difference. Quite the opposite. The diversity in human genetics is relatively small compared to other species. For example, quoting http://www.nature.com/ng/journal/v27/n2/full/ng0201_155.html : > The extent of DNA sequence var…

If human races (which clearly exist) are not genetically distinct enough to be considered subspecies, how about the inverse? Can you point out examples of animal species/subspecies that have races?

Are different dog breeds the equivalent of human races, for example?

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

#49

Post by danieltillett » Fri, Sep 09, 2016, 4:34 PM UTC

openasocket wrote: post #47

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.

If only it was! But then we discovered "ring species" ( https://en.wikipedia.org/wiki/Ring_species ) which threw a monkey wrench into what was once a simple definition. Basically, there are populations of animals A, B and C, where A and B can inter-breed, B and C can inter-breed, but A and C can't. So our definition of species no longer satisfies the transitive property, and it all falls apart. As far as I know, this…

A species is just a human construct to make it easier to understand biological diversity. In the real world living things are never black and white.

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

#50

Post by MustardTiger » Fri, Sep 09, 2016, 4:34 PM UTC

saynsedit wrote: post #29

MustardTiger wrote: post #16

Earlier quoted context omitted.

>The paper is about species, not subspecies. And my reply is about subspecies, and our refusal to apply the same standards we apply to other animals to ourselves. I do not understand your confusion. >Humans do not meet the phylogenetic criteria which justifies the use of "subspecies" We have greater genetic difference between races than ANY example of subspecies in existence. I am very aware that a large group of peo…

Physical difference is not the same thing as genetic difference. Humans may subjectively look very different but genetically humans aren't very different. This is empiracle fact. Stop living in the 19th century.

Physical difference has nothing to do with the discussion. That is a complete red herring you just pulled out from no where. The empirical fact is that humans are genetically quite different. The genetic distance between human races is greater than many species, and virtually all subspecies distinctions made in the animal kingdom. Stop denying science because of a false belief that lying will somehow get rid of racism.