3 ms·

"Homo sapiens originated about 200,000 years ago." That figure keeps changing, and it's so fascinating - fascinating enough that I wish they'd given a little m

by Vivtek 17y ago

"Homo sapiens originated about 200,000 years ago." That figure keeps changing, and it's so fascinating - fascinating enough that I wish they'd given a little more than the bald assertion of the current estimate as though it were long-established fact.

hugh3 17y ago
Aren't species boundaries pretty fuzzy when you start trying to look at them across time? A species is defined as a closed set of organisms which can breed with one another. I could breed with someone ten years older, they could breed with someone ten years older than them, and so on into the past until we have an unbroken chain of "could breed with" leading back to reptiles, amphibians, fish and invertebrates with whom I could most definitely not breed (and probably wouldn't want to). But there was no dividing line between "homo sapiens" and "something else" as we go up the chain; there couldn't possibly have been. I get the impression that palaentologists define species by macroscopic features in the fossils, but that they are forced to do so in a fairly handwavey way, so any date when "homo sapiens" really first appeared is pretty arbitrary.
- CWuestefeld 17y ago
  I think you're mostly right, except that the definition of species comes from does breed with, rather than could. Also, in your example, your ancestor of 10 generations ago cannot breed with one of his contemporaries but 10 years junior, because they're both dead. This isn't hair-splitting, it provides the practical answer to your question. There's no potential for mingling genetic material between those two organisms today.
- Vivtek 17y ago
  Yeah, but it's really germane to (what I consider) the real question, which is: "When did our path to history start?" I mean, it's a big difference if we had 150,000 years of prehistory, or a million, or 50,000.
  - hugh3 17y ago
    I really don't see what you mean by "our path to history"

by Vivtek 17y ago

hugh3 17y ago

Aren't species boundaries pretty fuzzy when you start trying to look at them across time? A species is defined as a closed set of organisms which can breed with one another. I could breed with someone ten years older, they could breed with someone ten years older than them, and so on into the past until we have an unbroken chain of "could breed with" leading back to reptiles, amphibians, fish and invertebrates with whom I could most definitely not breed (and probably wouldn't want to). But there was no dividing line between "homo sapiens" and "something else" as we go up the chain; there couldn't possibly have been. I get the impression that palaentologists define species by macroscopic features in the fossils, but that they are forced to do so in a fairly handwavey way, so any date when "homo sapiens" really first appeared is pretty arbitrary.

CWuestefeld 17y ago
I think you're mostly right, except that the definition of species comes from does breed with, rather than could. Also, in your example, your ancestor of 10 generations ago cannot breed with one of his contemporaries but 10 years junior, because they're both dead. This isn't hair-splitting, it provides the practical answer to your question. There's no potential for mingling genetic material between those two organisms today.
Vivtek 17y ago
Yeah, but it's really germane to (what I consider) the real question, which is: "When did our path to history start?" I mean, it's a big difference if we had 150,000 years of prehistory, or a million, or 50,000.
- hugh3 17y ago
  I really don't see what you mean by "our path to history"