Hacker News Reader

Comment by dalke | Hacker News Reader

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 the mitochondria or partial nuclear genomes) of polar and brown bears, and establishes the divergence of polar and brown bears at 400,000 years ago.

> ... However, because neither species can survive long in the other's ecological niche, and because they have different morphology, metabolism, social and feeding behaviours, and other phenotypic characteristics, the two bears are generally classified as separate species.[29]

View on HN

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 them the same species we just need to let the old scientists die off ;)

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.

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.

>The long term definition was more or less 'A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.'

No, that was one long discredited idea of species. It has not been used in decades. Why are you so insistent on pushing this false claim that brown bears and polar bears are the same species? Look it up, they are not. One is Ursus arctos and the other is Ursus maritimus. There is no ambiguity or dispute.

Reply on news.ycombinator.com