> 1. Humans have existed as a distinct species for about 200,000 years.
No, that's wrong. Humans, genus Homo, have existed for about 2.5 million years; the subspecies H. sapiens sapiens for about 200,000. The species H. sapiens is a little less clear, there's debate over whether it starts around 200,000 years ago (and includes just a few subspecies, notably H. sapiens sapiens and H. sapiens idaltu) or whether it starts around 500,000 years ago and includes several others.
> 2. Given the process of natural selection, in another 200,000 years we will have been replaced by something different than us -- not necessarily bigger or smaller, smarter or dumber, just different.
Unlikely; while speciation requires time, time alone is not generally enough, and even if it were, there is no reason to expect the time from the last speciation event to now (whether 500,000 years or 200,000)
to be the time from now to the next speciation event.
(Colonization of Mars -- if Earth-Mars interaction is limited once the colony is established -- might actually accelerate that, since the one thing that does contribute to speciation is geographical separation which prevents significant interbreeding between segments of the wider population.)
> 3. In a million years, there will be nothing remotely resembling human beings -- it will be as though we had never existed.
Human beings, genus Homo, have been around for two and half million years already, and H. sapiens (whether you take the narrower or broader view of the species) would be a flash-in-the-pan as species of its size, lifespan, and geographic range are concerned if it wasn't around for several million more (H. erectus -- with competing members of the genus Homo around on Earth for pretty much its whole time of existence -- lasted about 1.75 million years), and things "remotely resembling human beings" have been around significantly longer -- and can be expected to be around significantly longer than humans in the strict sense, unless humans are wiped out completely in a cataclysm rather than subjected to the kind of pressures that produce speciation.
> The sun will become a red giant and envelop the earth in somewhere north of five billion years, which is five thousand times longer than we can possibly exist as an identifiably distinct species, using the optimistic forecast of item (4) above.
The million year forecast isn't "optimistic"; while it may be unlikely that human beings would be around for 5 billion years, your particular argument for that point is, well, based on one controversial claim and a couple of unjustified claims that don't follow from that controversial claim.
> The million year forecast isn't "optimistic"; while it may be unlikely that human beings would be around for 5 billion years, your particular argument for that point is, well, based on one controversial claim and a couple of unjustified claims that don't follow from that controversial claim.
Where's the refutation of my point that we will have entirely disappeared in a million years, replaced by some other species? This isn't a philosophy debate, where words like "controversial" and "unjustified" carry weight among people trained in critical thought.
> Where's the refutation of my point that we will have entirely disappeared in a million years
Where's the support for the claim?
> This isn't a philosophy debate, where words like "controversial" and "unjustified" carry weight among people trained in critical thought.
"Unjustified" always carries weight among people trained in critical thought, at least, when its true -- i.e., no adequate support has been provided for the conclusion presented. You've simply asserted that humans have been around for only 200,000 years as a species (which is one of two common viewpoints about H. sapiens, though "humans" in this context usually means the genus Homo and not the species H. sapiens -- 500,000 is the other, because where exactly at what point H. sapiens becomes a distinct species is debated), and jumped from there to the conclusion that H. sapiens will be replaced in another 200,000 years and that nothing similar will be around in a million years. Neither of those conclusions follow from the premise, which itself is less-than-certainly correct.
No, that's wrong. Humans, genus Homo, have existed for about 2.5 million years; the subspecies H. sapiens sapiens for about 200,000. The species H. sapiens is a little less clear, there's debate over whether it starts around 200,000 years ago (and includes just a few subspecies, notably H. sapiens sapiens and H. sapiens idaltu) or whether it starts around 500,000 years ago and includes several others.
> 2. Given the process of natural selection, in another 200,000 years we will have been replaced by something different than us -- not necessarily bigger or smaller, smarter or dumber, just different.
Unlikely; while speciation requires time, time alone is not generally enough, and even if it were, there is no reason to expect the time from the last speciation event to now (whether 500,000 years or 200,000) to be the time from now to the next speciation event.
(Colonization of Mars -- if Earth-Mars interaction is limited once the colony is established -- might actually accelerate that, since the one thing that does contribute to speciation is geographical separation which prevents significant interbreeding between segments of the wider population.)
> 3. In a million years, there will be nothing remotely resembling human beings -- it will be as though we had never existed.
Human beings, genus Homo, have been around for two and half million years already, and H. sapiens (whether you take the narrower or broader view of the species) would be a flash-in-the-pan as species of its size, lifespan, and geographic range are concerned if it wasn't around for several million more (H. erectus -- with competing members of the genus Homo around on Earth for pretty much its whole time of existence -- lasted about 1.75 million years), and things "remotely resembling human beings" have been around significantly longer -- and can be expected to be around significantly longer than humans in the strict sense, unless humans are wiped out completely in a cataclysm rather than subjected to the kind of pressures that produce speciation.
> The sun will become a red giant and envelop the earth in somewhere north of five billion years, which is five thousand times longer than we can possibly exist as an identifiably distinct species, using the optimistic forecast of item (4) above.
The million year forecast isn't "optimistic"; while it may be unlikely that human beings would be around for 5 billion years, your particular argument for that point is, well, based on one controversial claim and a couple of unjustified claims that don't follow from that controversial claim.
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