Your response is very good. It is always safer to believe facts than it is the theories that are based on them. And a simple theory, such as “white swans exist” can be substantiated by the sighting of one, or at the most two, white swans.

However, I think that you miss two at least theoretically important points. The first is that you have not truly gotten back to facts. The second is that even apparent facts can be questioned.

For example. to take the second point, it was commonly believed at one point that in human evolution, the brain became enlarged first and the jaw became more human later. This seemed to be substantiated by a skull and jaw found in Piltdown. A closer examination of the “fact” revealed that the skull and jaw were in fact modified modern human and orangutan, respectively, and the “fact” evaporated, along with the theory built on it.

So when you say, “Hominina lived outside Africa at least 2 million years ago.” you are presumably basing this on physical evidence. Let’s say, for the sake of discussion, that we have one skull dated at 2 million years, and another 3 skulls dated at 1.5 million years. If someone were to show that the skull dated at 2 million years had a carbon-14 to ordinary carbon ratio comparable to that of modern humans, or even comparable to an uncalibrated radiocarbon age of 35,000 years, you would then have to revise your statement to read “Hominina lived outside Africa at least 1.5 million years ago.”

To take the first point, you would have been safer if you had said, “Hominina lived outside Africa at least 2 million years ago, by currently accepted dating criteria.” For a date is not a fact stamped on the rock and readily available for all to see. It is a series of measurements, with their inherent uncertainties, along with a theory that interprets those measurements as an age. The theory could ignore sources of error, which could theoretically be large enough to invalidate the age.

If we were to discover sources of error that could explain all the dates to which you had reference in your list, we could no longer accept your assertions as valid. And if we had another secure dating method that argued that the timescale was inflated by orders of magnitude, all of your assertions would be wrong.

I am not arguing here that this is the case at present (although there is interesting evidence that it may be the case), but only arguing that we need to be careful about pronouncements in science.

However, there is one final area that should be mentioned. Science is rarely so easily falsified as a straightforward application of Popper would imply. As mentioned by Truthzyme (#30), science is an interconnected web with resilience, and it is rare that a single fact will completely destroy that web. This is partly because the weight of theory will oftentimes result in extra scrutiny of apparently contrary facts, so that the facts are often shown to be based on misunderstanding or fraud, and not what they seemed at first. A theory may even simply put the facts on a shelf, to be studied and integrated later when more is known. And finally, a theory can be used to rule certain facts invalid or inapplicable, even when the facts should rightfully overthrow the theory. It takes a strong theory to do this. But naturalistic evolution is such a strong theory.

So the answer to Denyse’s question is that there is probably not one single observation that would invalidate most assertions about human ancestry. But with a suite of observations, practically any given assertion could be overturned.

This is a proposed a quality, or fact, about observable evolution. It is not the same as a rote fact about humanity (brain capacity etc.). It is not shown that damaged DNA has produced any quantifiable or observable trait except those involving defects, however there is a direct and provable correspondence between altered DNA and the consequences listed above.

Notice any claims of beneficial mutations (I know, but pretend with me) do not undo this claim since undesirable effects are certainly observed. The reverse is not true, as the idea of beneficial mutations stands to be disproved as a statistical impossibility as the complexity of the information found in DNA becomes more evident. The other way to reverse this observation would be to claim that human DNA in the past was not changeable, but that ends the debate anyway.

Consequently, a finding such as that, would overturn, not just evolutionary science, it would overturn ALL of science.

But the question isn’t quite that, it asks “what do we really know about human evolution that could not SIMPLY be overturned by a new find?”

What we really know about human evolution should not be considered as a linear list of independent facts. The essence of our knowledge lies with the vast web of interrelations that is draped across the conventional divisions of the constituent subjects of science. The famous evolutionary scientist O. E. Wilson called it Consilience: The Unity of Knowledge in his book that name. Wilson explains:
“Literally a jumping together of knowledge by the linking of facts and fact-based theory across disciplines to create a common groundwork for explanation.” (page
Scientific knowledge is “holographic” and it “all hangs together”. By its very nature, it is able to take multiple fixes from different angles on any issue. Consequently, vital dependence on one particular fact is rarely, if ever, encountered.
So what we know about human evolution is a subset of that vast consilient network, and, like a spider’s web it is also resilient to the weakening or removal of any one of the many facts and theories upon which it depends. In a world free of miracles and unexplained effects, that is how it must be, that is the only way it can be. Unless of course we are being subjected to that diabolical simulation constructed for the amusement of some mischievous super-alien.

Darwin correctly conjectured that humans and the African apes had a common ancestor.

In the last decade, “what we know about human evolution” has been refined and extended by advances in Evolutionary Psychology and in the analysis of the vast historical records to be found in the DNA of primate species. Consequently, “what we know” is not just a fact or even a list of facts, it is a theory that ties all the facts together and shows how they interrelate. It is this theory that cannot be SIMPLY overthrown by a “new find”.

Glad you liked the post. I’m sure Denyse won’t have a problem with it. Affirming common descent for humans and chimps does not entail that the differences betwen them can be explained by natural selection alone.

JayM,

A simple yes or no will suffice.

That’s not what kairosfocus told me.

JJ

A simple yes or no will suffice.