How could evolution be disproved?

First a disclaimer: I believe the theory of evolution is correct, or largely correct. I’m not a proponent of creationism or intelligent design.

That said, one of the arguments I’ve used against people claiming that intelligent design is a science is that there isn’t any possible experimental result that would prove intelligent design false. So my question is: What experimental result would prove the theory of evolution false?

I am not a biologist, but I imagine that with the discovery of genes, if it had turned out that different species encoded traits in radically different ways, or a genetic makeup that was fundamentally different in structure from each other, this would have proved that the differenct species do not share a common ancestor, and are not related to each other. So investigation into DNA turned out to be an experiment that would have disproved evolution, but which turned out instead to provide even more evidence for the theory.

As for experiments which haven’t already been done, I’ll have to leave that to people who, unlike me, actually know what they are talking about.

Supposing we sequenced the DNA of a slamander, and found that it was more closely related to humans than humans are to chimps. That might not disprove evolution, but it would throw a huge wrench in the works.

Now, supposing this sort of thing happened again and again and again.

If radioactive dating techniques showed that the Earth was only 10,000 years old, that would disprove evolution. There wouldn’t be enough time for it to occur.

If you want to browse throughthis thread you will find a discussion of whether evolution is falsifiable. Interesting stuff.

If verifiably authentic hominid fossils were found sharing strata with dinosaur fossils, it would disprove or cause a serious re-evaluation of evolution.

If verifiably authentic fossils of Homo sapiens were found in earlier strata than, say, the Lucy fossil, it would disprove or cause a serious re-evaluation of evolution.

One of course would be that if the fossil record showed that the species that occur today all originated at the same point in time in the past and have persisted since that time essentially unchanged. Another would be the lack of clear anatomic and genetic homologies between organisms.

But there are many possible lines of evidence that would indicate special creation was true, instead of evolution, if in fact that were the case. In fact the evidence is overwhelming that evolution has occurred.

But that’s not the problem with intelligent design. The proponents of intelligent design don’t deny that organisms have evolved, they only propose that this evolution has been guided by a external intelligence. There is no way to prove or disprove that particular contention, and this the reason that intelligent design is not science.

Not really. We’d have to rethink the timetable, that’s all.

We don’t know that Lucy’s species was ancestral to us. In fact, we don’t know which species that existed 3M years ago was ancestral to us.

Spontanious species change would also require a complete reworking of the Evolution theory. If a pair of goats mated and produced a gyraffe or a creature as biologically different to goats as a gyraffe is. This would make steady change evolution seem unlikely to be the main path of evolution. Similarly (and linked to a fun GQ question) if X-Men started appearing as natural human evolution a similar reapraisal of steady change evolution would be necessary.

Yes, most people do beleive that evolution does happen, I think you need to prove that the chain from single cell beaties to the complex animals we have today have impossiable jumps (with out help). I’ve heard that the development of sexual reproduction is often stated as one of these impossiable jumps.

If fossils of true Homo sapiens were unequivocally found in strata together with dinosaurs, it would be better evidence of the possibility of time travel than it would be that evolution was false. The mass of evidence for evolution is so overwhelming and from so many different sources that it would be difficult to dismiss even in the face of an anomaly of this kind.

My attempt at a holistic answer to the OP. “Evolution” as a whole isn’t so much a single theory as the the inevitable outcome of some underlying ones. So I think you’d have to falsify one of them.

Evolution in this scientific sense is basically six postulates: three genetic ones, and three environmental ones.

The genetic ones:

  1. Offspring inherit traits from their parents. (Inheritance)

  2. At least occasionally, offspring will manifest a trait not inherited in any parent (Mutation).

  3. A certain amount of similarity is required for one organism to produce offspring with another (Speciation). Stated in the negative, sufficiently different organism will not, and–if the difference is large–cannot, have children together.

The Environmental ones:

  1. Certain traits increase or decrease life expectancy in specific environments.

  2. Statistically over large numbers of organisms, organisms which live longer have more offspring.

  3. Environments change over time and/or space.

Everything else follows from these six. So to falsify evolution, you need to either:

  • Demonstrate that one of these six is false, or
  • Demonstrate that another condition is necessary, AND demonstrate that it’s false.

The usual one to attack is (3), which requires demonstrating that a large number of observed speciation events are faulty or not reproducible


More accurately, “anti-evolution” proponents generally attack combinations of them: “Sure, changes happen, but they don’t add up” or “Things can change, but never so much that speciation happens” or “Environments don’t change enough to cause speciation” or the positively bizarre: “Sure, some creatures are evolving, but most don’t.”

To answer a couple other points raised here at random:

Colibri, it has been my experience that proponents of Intelligent Design generally do deny that organisms have evolved, but it’s a quibble. More importantly, I think, is that their postulate is stronger than you stated. Specifically, that the evolution of complexity (usually stated as intelligence) REQUIRES design by a designer of greater (or at least equal) complexity. This axiom is trivially shown false by failure of induction. There’s no base case, God (or whoever) would have had to have been designed by a still greater intelligence,and so on. The introduction of the idea that “God is an exception” is religion, nonfalsifiable, and another point at which ID ceases to be science: it’s the redundant “introduced” non-created being necessary in the first place only because we don’t accept the universe itself being non-created.

kanicbird The sexual reproduction one is pretty easy, actually: once the work of “constructing” the fetus has been differentiated to different cells (which occurs even in asexually reproducing creatures), there’s no barrier at all to the different parts being in different creatures. The whole penis/vagina thing would take a while to develop, but simple proximity sharing of genetic information (by rubbing, pollination, separated laying/fertilizaton events (like fish), actual intermingling of two organism, etc.) is easy, and everything after that is just a jump.

In fact, assume you’ve got an organism with both “male” and “female” genetic material (which exist), and a relatively easy way to share it with those organisms around it, such as these

Once you’ve got that, losing the ability to asexually reproduce might not be be a disadvantage if breeding partners are readily available, so a mutation that caused an either/or creature to be sexually reproductive only wouldn’t necessarily select against them.

There’s some interesting papers on this on the web, but I can’t find one that’s just HTML and not PDF or Powerpoint, so just google on “both sexual and asexual”. Oddly enough, this seems to be a mostly work-safe search :dubious:

Possibly, but Intelligent Design as a concept does not require rejection of the fact that organisms have evolved. Of course, since it is creationist in inspiration many of its proponents may in fact deny this, as you say.

True, but I wasn’t trying to give a complete critique of the idea. Thanks for providing more detailed information on some of its problems.

Whatever came along and supplanted evolution as (by far, or indeed the only)the leading scientific theory explaining the diveristy of life, would have to incorporate explanations for the mountains of extant data; for example, why species that appear morphologically similar in detail also appear genetically similar, share traces of what looks like ancestral virus infection, are geographically distributed as if they spread out from a single point, etc; it would have to explain why weeds develop resistance to herbicides, why bacteria develop the ability to metabolise plastics, it would… well… I could go on and on and on, but I’m sure you get the point.

At this stage, there’s just ssuch an enormous wealth and diversity of compelling evidence, all of it pointing the finger squarely at evolution, it’s hard to imagine any way it could be toppled; this doesn’t mean evolution is logically unfalsifiable, it just means it’s unlikely to be proven false, because it actually looks for all the world that it’s true.

IMO, the most likely way evolution could possibly turn out to be false is if it somehow turns out that we’re all living inside a computer simulation that’s been specifically set up to foster the illusion that evolution has happened and continues to happen.

Well, that, or else if Last Thursdayism is true.

Same difference, mostly. Although I’m not sureif we could ever know that we’d been last-Thursdayed, so evolution would probably stand.

Well, evolution is a complex activity, but one part of it is natural selection. I suppose that if one put a species under some form of natural (or artifical) selection and the species did not evolve in the expected manner, that would be a data point against evolution. Certianly not conclusive, since a species can only respond to stress through mutation and in the experiement it may be that the secret solution to the stress just didn’t show up in time. I believe that is called extinction. So my hypothetical experiment would have to designed to avoid that problem say increasing the natural mutation rate or conducting the experiment many times. But in principle one could design an experiment (I think I am not a biologist) that would prove natural selection. If the experiment gave a different result, then that would be a hit against evolution. Don’t thing it is feasable or that it natural selection whould fail to work, but you asked for an example.

It’s hard to prove a negative.

Thanks to everyone for your fascinating and insightful responses.

Actually, in the case of a scientific theory, I’d say it’s much easier to prove a negative – i.e., to disprove the theory. Disproving a theory just requires you to demonstrate that its predictions are false, whereas proving a theory would, I suppose, require you to demonstrate not only that its predictions are true but that it is the only reasonable explanation for those results. In the case of evolution, it’s hard to prove the negative probably because the negative is wrong.

There’s one really simple observation that would falsify evolution.

Find an example of a heritable trait that has changed within a population with no concommitant change in genetic frequency within that population. Its reallly that simple.

Find for example a breed of dog that has changed colour while remianing essentially genetically identical to the ancestral population.
There were some trivial exmaples of that sort of thing poccuring discovered in the mid 90s but they turned out on closer inspectionto be the result of prion shepherding of the DNA/RNA. SO far no one has found an example of a heritable change in populations that wasn’t genetic.