Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

researchgate.net

Post reply on HN
Print view View original

61–70 of 107 posts

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

#61

Post by rrauenza »

danieltillett wrote: post #49
openasocket wrote: post #47

Earlier quoted context omitted.

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.

...except Zebras?

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

#62

Post by frozenport »

dschiptsov wrote: post #59
alexbock wrote: post #34

Earlier quoted context omitted.

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.

So, are there different species of people?)

Not if you consider alcohol.

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

#63

Post by MustardTiger »

Dylan16807 wrote: post #53
MustardTiger wrote: post #50

Earlier quoted context omitted.

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 racis…

Humans have accumulated an enormous amount of genetic variation between groups in only a few thousand years? Citation needed.

http://www.nature.com/ng/journal/v36/n11s/full/ng1435.html

You can barely even discuss the facts much less publish them because of histrionic accusations of racism and eugenics. Also, it hasn't been a few thousands years, it has been tens of thousands of years at the low end.

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

#64

Post by kristofferR »

sandworm101 wrote: post #37
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...

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.

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

#65

Post by dalke »

dogma1138 wrote: post #45
dalke wrote: post #43

Earlier quoted context omitted.

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 o…

My definition is: has it been assigned a binomial name? I'll also accept if the process has started.

The PNAS paper for the first event does not give a binomial. It says:

> We treat the endogamous group as an incipient species because it has been reproductively isolated from sympatric G. fortis for three generations and possibly longer.

I was not aware that this was the accepted common definition of a species.

The second also does not give a binomial. It describes a method to "initiate evolution of reproductive isolation among sympatric populations".

Is that enough to say that there is a new species? If so, I was not aware that the threshold for a species definition was so sensitive.

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

#66

Post by danieltillett »

rrauenza wrote: post #61
danieltillett wrote: post #49

Earlier quoted context omitted.

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.

...except Zebras?

Even zebras are not black and white - more a dark brown and cream ;)

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

#67

Post by Dylan16807 »

MustardTiger wrote: post #63
Dylan16807 wrote: post #53

Earlier quoted context omitted.

Humans have accumulated an enormous amount of genetic variation between groups in only a few thousand years? Citation needed.

http://www.nature.com/ng/journal/v36/n11s/full/ng1435.html You can barely even discuss the facts much less publish them because of histrionic accusations of racism and eugenics. Also, it hasn't been a few thousands years, it has been tens of thousands of years at the low end.

>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, approx90% of total genetic variation would be found in a collection of individuals from a single continent, and only approx10% more variation would be found if the collection consisted of Europeans, Asians and Africans.

>The pi value for Homo sapiens can be put into perspective by considering that humans differ from chimpanzees at only 1 in 100 nucleotides, on average14, 15.

> Clustering of individuals is correlated with geographic origin or ancestry. These clusters are also correlated with some traditional concepts of race, but the correlations are imperfect because genetic variation tends to be distributed in a continuous, overlapping fashion among populations.

I'm not sure how this supports your point. What species are separated by a pi value of 1 in 10000 or less?

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

#68

Post by Retric »

danieltillett wrote: post #57
Retric wrote: post #31

Earlier quoted context omitted.

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.

I don't think there is any good evidence for Australia being populated before 45,000 years ago. Modern humans hadn't even left Africa 75,000 years ago.

Your dates for leaving Africa seem to be off base. Homo sapiens ventured out of Africa around 100,000 years ago https://en.wikipedia.org/wiki/Early_human_migrations

There where early tool across Afro-Eurasia as far back as 1.7 to 2.6 million years. Early human ancestors may have maintained separate populations spreading genetic mutations between them with occasional waves of migration displacing existing populations. Supporting the first idea is the wide range of habitat giving advantages to prior populations who are better able to cope with existing conditions. http://www.nature.com/news/teeth-from-china-reveal-early-hum...

There really does not seem to be much evidence to tell one way or another.

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

#69

Post by jacobrobbins »

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.

the philosophical questions raised by multiple, visually similar species being considered as one have come up before. Zebras were discovered to be 3 separate species. See "What, if anything, is a Zebra?" from 1983 http://polaris.gseis.ucla.edu/gleazer/462_readings/gould.pdf

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

#70

Post by Retric »

MustardTiger wrote: post #56
Retric wrote: post #21

Earlier quoted context omitted.

People also talk about Europe and Asia as separate despite being a contiguous landmass on the same plate. Genetically brown and polar bears can and in reality often do interbreed producing viable offspring and exchanging genetic information between populations.

>People also talk about Europe and Asia as separate despite being a contiguous landmass on the same plate That analogy is not useful at all. Continents are not biological organisms. >Genetically brown and polar bears can and in reality often do interbreed producing viable offspring and exchanging genetic information between populations And yet they are separate species. Just like the 4 separate species of giraffe the…

The point which is very clear that people stick with old definitions despite new evidence even in the sciences. The great thing is different countries use different definitions yet people seem to assume whatever they grew up with is correct. https://en.wikipedia.org/wiki/Continent#/media/File:Continen...

At most you can say brown and polar bears are "generally classified as separate species" But, there really is debate on this topic.

Post reply on HN