Interested in Proof of Macroevolution

Great Debates
1

I am interested in seeing proof of macroevolution. Allow me to explain my motive …

I’m a Christian, but not a fundamentalist in the traditional sense. I believe in the biblical creation account, but I don’t think that even a fairly literal interpretation (other than the use of the words “day”, “morning”, and “evening”, which don’t make any sense if interpreted in the common 24-hour manner) requires a young earth. Therefore, all of the anti-creationist arguments regarding the age of the earth are just fine by me. I’m more interested in reconciling the creation of “kinds” and the account of Adam and Eve with the theory of common ancestry. I firmly believe that there should not be a conflict between my beliefs and what can be proven by science. However, while I have seen the pretty clear-cut evidence of microevolution, or adaptation, as I prefer to think of it, I’m still pretty fuzzy on the proof for macroevolution, particularly the idea that all living things, including humans, share a common origin.

A few years ago I did a fair amount of research and came away unsatisfied. I always ended up feeling like the proposed theories were built on unproven card-houses, and it seemed like it was easy to cut the legs out from under the accepted solutions. But I’m also fully aware that many honest, intelligent people with far more experience than I have labored over these topics for decades, and I’d really like to see what it is that I’m missing. So, since these forums seem a likely place to find people who can weigh in on this topic … show me what you got.

Although it may be hard for me, I will try not to refute anything you present, although I may ask a few questions.

2

Proof?

Sorry, but that’s never going to happen. The best one can hope for is strong evidence based on a preponderance of observations.

Since evolution takes place over millions of years, the only evidence is fossil records and the resulting species. There is also genetic evidence, but none of this is irrefutable proof.
However, the theory seems to fit the available facts pretty well.

3

What sort of proof are you looking for? Obviously nothing can be shown to you in real time.

I would start with comparing the similarities between humans and chimps, then chimps and monkeys, and so on, working your way back. The path from humans to sea life seems pretty easy for me to grasp.

4

I never really understood this. How can you agree with “microevolution” but disagree with “macroevolution”. I mean, if a species keep on microevolving through millions of years, will that not lead to larger changes in that species, which is macroevolution?

5

If you weren’t convinced by your reading, then I don’t see how you are going to be by anything said here. The evidence for macro evolution includes observations in physics, geology, chemistry, and biology.

Looking at geological strata you can see that fossils of simpler life occur beneath those of more complex life (allowing for upheavals, etc.). Radioactive dating of any number of elements shows the relative age of deposits. The age of rocks can also sometimes be determined by the magnetic pole information laid down in rocks as they cooled. Analaysis of DNA shows the relation between various species and it corresponds very well with the family tree determined by more traditional methods of comparing like structures in fossilized life forms.

Almost our entire knowledge of the physical sciences would have to be overturned by the presumption that man and other creatures were each created separately as they exist now, rather than gradually evolving over time from common ancestors.

On the other hand, you have a book with no evidence that it was dictated directly by God, that describes one sequence of events of creation. It is just one creation story of many, most of which contradict one another. There is no more or less evidence for the Biblical story than there is of Native American creation accounts.

6

Hope this isn’t considered a hijack; it’s tangentially relevant to your question.

You are looking for “proof” of macroevolution. Do you always require “proof,” when deciding whether to accept a belief?

Did you require proof when you decided to believe in God, or the devil, or angels, or the hereafter? Can you prove that you have a soul? Can you prove that Jesus died for our sins? Can you prove that the Bible is the word of God?

Why do so many religious people require proof of evolution, and nothing else? If you can believe in so many things, based on faith, why can’t you have faith in evolution?

7

“Microevolution” and “macroevolution” are phony, Creationist distinctions. It’s all the same thing. macro is just a whole bunch of micro. Saying you can accept micro but not macro is like saying you believe hair can grow one inch but not two inches. It’s the same thing. What do you imagine would stop “micro” events from leading to speciation?

8

[QUOTE=timtupp]
However, while I have seen the pretty clear-cut evidence of microevolution, or adaptation, as I prefer to think of it, I’m still pretty fuzzy on the proof for macroevolution, particularly the idea that all living things, including humans, share a common origin.
[/QUOTE]

For starters, there are an awfully large number of living animal groups that bear remarkeable resemblance to other living groups. As mentioned above, for example, there’s the human-chimp comparison. Under Special Creation there is no (as in zero, zilch, nada) reason or explanation why these two allegedly separate and distinct groups should share any similarities, much less the large number of similarities that they do share. Those sorts of observations are common throughout the animal and plant worlds (and, of course, the same holds true for all living things).

Now, factor in the fossil record. Here, we have vastly more organisms which we can examine and compare to existing groups. And we still see the same pattern: extinct groups represented in the fossil record share remarkeable similarities with living groups, and with each other. The degree of similarity between fossil and living organism may decrease as one goes further back in the fossil record, but almost always there are at least other fossil groups which maintain a remarkable degree of similiarity to the fossil being examined.

The conclusion, then, when coupled with the knowedge that organisms do change over time, is that these seemingly separate groups we see today, and in the fossil record, are related by descent.

Now, one can argue that similarity in form is a natural consequence of similarity of function, and that this is sufficient to explain any superficial similarities we see between organisms today, or between living organisms and extinct fossils. The problem is that we can construct trees of similarity, similar to one’s own family tree but on a much larger scale, that is completely independent of function – and those trees themselves can be unified into a single, larger tree comprised of all living things. If function were the primary producer of such similiarities, then we would expect to see multiple, independent trees, based on lifestyle. Birds, bats, and pterosaurs ought to group most closely together; grazing mammals ought to group more closely with grazing reptiles than to whales; and so on. Most importantly, there would be no unification possible between those trees - which is not at all what we see at all. Further, at the genetic level, we see what appear to be selectively neutral sections of DNA which are remarkably conservative among groups which we have otherwise presumed to be related by descent. Again, this is not at all an expected result of Special Creation.

Consider this image: http://news.bbc.co.uk/2/shared/bsp/hi/pdfs/28_03_07_mammalstimeline_pdf.pdf

(It’s a .pdf document, obviously)

This is a what is known as a “supertree” for all major mammal groups, showing their relationships and relative times of divergence, based on a) the assumption of common descent and b) similiarities found via multiple modes of inquiry (e.g., morphological, genetic, etc.). Were common descent mere fiction, such an image would be impossible to create.

Here is another supertree, this time for all major dinosaur groups. Again, such a thing would not be possible if common descent were not the case.

Then you have projects like this, which attempt to unite all those trees into a single, gi-huge-ic Tree of Life. Again, this would be an impossible task if all these various groups were not, in fact, related by descent from one another.

In the end, there is no single piece of evidence that allows us to state definitively that all life is descended form a single common ancestor which appeared some 3.9 billion years ago. It is a conclusion based on numerous lines of inquiry regarding the “whys” of similiarity between extant and extinct forms.

Once you get past this most important hurdle, the rest of the macroevolutionary concepts (e.g., speciation, diversification, extinction, evolution of novel structures, etc.) fall into place quite neatly.

9

A recent issue of Scientific American approached the issue of a common origin of life by looking for signs of the converse: that some life exists that doesn’t share a common origin with all the rest. Are Aliens Among Us? by Paul Davies

The article shows that despite the best efforts of scientists, no form of life, no matter how extreme the conditions, has ever been found that shows a second independent origination point.

The underlying point is that having once emerged, the common form of life would simply out-compete any newcomers unless they retreated into areas where other life could not follow or were built on principles that exploited resources that known life could not utilize.

One of the commonest techniques in mathematics is to try to prove the converse of your theorem and show that it leads to a contradiction or an impossibility. Most other sciences have few opportunities to go down this route. Failing to find non-common life is a fascinating indicator of how interrelated all known life must be.

10

The strongest evidence of common origin and the nature of inheritance and variation of characteristics is via the mechanism that Darwin did not have access to in his day; the genome. Although Gregor Mendel demonstrated the principles of inheritance, Darwin was not aware of his studies, and in any case it wasn’t until Theodor Boveri and Walter Sutton, working in the early 1900’s, identified the chromosomes as the carriers of Mendelian alleles (units of inheritance of phenotypes or expressed characteristics), and Thomas Hunt Morgan famously demonstrated this (picking up a Nobel Prize in the process) with the common fruit fly Drosophila melanogaster, since become a favorite of those working in the field of genetics for its rather discrete allele structures and ease of breeding. The definitive work on modern evolutionary synthesis (the combining of the various fields within biology into a framework connected by the organizing concept of evolution and the underlying theory of natural selection) didn’t occur until the 1930’s when biologists like R. A. Fisher, J.B.S. Haldane, Julian Huxley, Ernst Mayr, Sewall Wright, Theodosius Dobzhansky, and many others started to piece together the actual structure of the field with detailed hypotheses supported by observational and experiemental evidence.

For anyone who knows about modern molecular genetics, it’s simply impossible to deny that organisms share a common core of genetic code, often to an amazing degree; even comparisons between different phyla (a taxonomic rank below kindoms like Animalia) demonstrate a large degree of genetic commonality, and within genus the difference in genetic content of the genome between one species and another is on the close order of a percent or less. Furthermore, it is possible with modern gene sequencing methods to examine and compare the genomes of both extant and extinct species and make an accounting of the differences and commonalities. This clearly demonstrates a line of progression and divergence between species and their presumed antecedants which typically correlates quite well with mophological fossil classification (and where it doesn’t often results in a correction to the fossil record).

The saltation-created “hopeful monster” (a new species created by massive, overarching changes to the genome) that would be inexplicably too complex of an alteration to have occured naturally has never found, and such a spectre (often raised by those trying to make a definitive distinction between microevolution and macroevolution, or trying to argue that the differences between species and/or completeness of various characteristics are irreducibly complex) is in reality a strawman; what we find from a genetic examination of the fossil record–where it exists in some semblence of completeness–is indeed a gradual modification of the genome and corresponding additions from mutation and drift that are adopted piecemeal, evolving characteristics gradually and separating from an existing species group by some method of reproductive isolation.

I realize I’ve thrown out a lot of technical terms, to which I’ve attempted some brief explanation; however, the above rationale probably won’t satisfy you if you are, in fact, completely unschooled in genetics and molecular biology. What simple, pat, brief, definitive argument or example can I give you that the mechanism of natural selection and the overall framework of evolution are true? I can’t, any more than I can give you a one page summary of the history of the Balkans, or explain the mechanism behind gyroscopic motion without going into far more detail and demanding you to learn the pertinent underpinning knowledge. If you are predisposed to disbelieve that evolution even occurs because you can’t observe or experiement with it in your kitchen sink, then nothing anyone will write on a message board will convince you otherwise. (Note that evolution and the science behind it itself says nothing about abiogenesis–the origin of life–only about the progression of modification, and so at least in that sense is not in direct conflict with a liberal reading of divine creation. Nor can it dispute claims that all events that occur are driven by some unseen architect, operating via mysterious unobservable interactions; it can only demonstrate the lack of necessity for such.)

However, if you are sincerely interested in learning about the science behind the theory of natural selection–if only to better argue it–may I suggest reading Earnt Mayr’s What Evolution Is (a detail summary of evolutionary theories), followed by some of the essays of the highly readable Stephen J. Gould? (The Richness of Life is a good place to start.) If you get that far, I’d then recommend reading something of Richard Dawkins, a “neo-Darwinistic” promoter of gene-centric interpretation (that genes are the essential units of selection), which while still being firmly under the banner of natural selection is in many ways in competition with the more holistic interpretations of Mayr, Gould, et al.

As for contrasting the “house of cards” of scientific theories regarding evolution against the creation story of the Biblical book of Genesis and the inception of Adam and then Eve (from Adam’s rib), I can offer nothing other than to note that no one can objectively demonstrate that the story is anything but fiction, and that no physical record of those characters and their offspring remain for inspection or analysis. The story (or rather, I should say, stories) of Genesis are certainly at odds with both our understanding of the origin of the Earth and life upon it, such as they are, and also in literal interpretation dramatically contradicted by our current knowledge of physics, geology, biology, et cetera. One can make the case that an looser interpretation still roughly conforms to our current understanding of the natural world, but I fail to see what that offers from a scientific point of view beyond the comfort that what you have accepted on faith still fits within an objective understanding of nature. To paraphrase Niels Bohr, it is wrong to think that the task of science is to find out how nature is. Science concerns what we can say about nature. Faith–religious or otherwise–stands outside of that.

Stranger

11

I’m sorry I can’t find a cite, but I read somewhere about geneticists researching groups of genes that seem to be responsible for gross morphological changes in body structure. By examing different genomes, they think they’ll be able to recreate the successive chain of mutations in these genes that occurred as organisms evolved. Creationists like to say that “evolution can’t turn a mouse into an elephant”; but in the near future it may be possible to compare the genomes of all classes of mammals for instance, and specify exactly how a small archtypical ancestral placental mammal could evolve into all the different species found today.

12

I’m going to go out on a limb and move this from General Questions to Great Debates.

Gfactor
General Questions Moderator

13

While I agree that the distinction between microevolution and macroevolution is spurious, I’m curious about what the OP considers macroevolution to entail. If it is simply speciation, there are plenty of more or less real time examples. If it is larger changes, then we have to work on the evidence. Biblical “kinds” is not well defined - and in any case if he is not a YEC even the creation of multiple kinds to begin with doesn’t mean that they couldn’t have speciated further later.

14

[QUOTE=timtupp]
I firmly believe that there should not be a conflict between my beliefs and what can be proven by science.
[/QUOTE]

That requires modifying your beliefs when science proves them wrong. The old testament creation account sounds suspiciously like the sort of rubbish ignorant primitives would come up with to explain the cosmos. None of it jibes with scientific investigation and evidence. You’re already willing to ignore the “days” mentioned in Genisis, yet you hold on to god creating the animals whole?

15

I’ve always found 29 Evidences for Macroevolution to have a nice overview of the types of evidence for macroevolution.

16

I think it might be worthwhile for you to define the difference between “micro” and “macro” evolution. As other posters have pointed out, evolution is a gradual process. If you believe that small changes are taking place, what is there to stop them from accumulating into larger changes? Be specific.

If you can’t see how small changes could lead to different species, you might be surprised to know that speciation has been observed in a laboratory.

17

I would say that one of the most straightforwardly conclusive evidences for common ancestry of extant lifeforms is endogenous retroviruses - in a nutshell, it works like this:

-A retrovirus inserts its own DNA right into a host cell - from that point onwards, the DNA in that cell carries a conspicuous, identifiable and more or less indelible trace of the infection.

-The insertion is not site-specific, so two infection events by identical viruses, on identical cells, are incredibly unlikely to end up inserting their trace in the same place in the host genome - each inserted trace is - for all practical purposes - unique.

-If that host cell happens to be a germline cell - that is, one that is responsible for the manufacture of sperm or ova, then those gametes will also carry the DNA trace

-If one of those gametes happens to be lucky enough to take part in the formation of progeny, then every cell in the offspring organism will bear the trace of the retroviral infection.

Therefore, if we find a trace of the same retrovirus, in the same location in the genome of two individual organisms, it’s most likely to be (and by ‘most likely to be’, we mean ‘hugely, astronomically improbable not to be’) there because those two organisms share a common ancestor - the ancestor whose germline cell was infected at that specific site by the retrovirus.

Now, the interesting thing is that we do find these traces - humans share a lot of them - humans and chimpanzees share fewer (but still quite a number), humans, chimpanzees and other primates share fewer still, and so on - and it turns out that mapping these shared traces organises them all into a tree of common ancestry that resembles - very closely - that which could be constructed by other, independent evidences such as comparative anatomy, the fossil record, geographic distribution, etc.

18

Oops. Missed the edit window with something else I wanted to add:

-I realise I didn’t mention macroevolution specifically anywhere in that post - this is in large part because it’s a term of disputed meaning - and too often, threads like this end up pussyfooting around trying to define exactly what it means - and where ‘micro’ gives way to ‘macro’. This, I believe is a wholly unnecessary distraction - we have compelling evidence for the common ancestry of primates, including humans - and I think that’s as ‘macro’ as it needs to be in this debate.

19

**Brazil finds fossil of crocodile ‘missing link’ **

20

[QUOTE=Stranger On A Train]
The strongest evidence of common origin and the nature of inheritance and variation of characteristics is via the mechanism that Darwin did not have access to in his day; the genome. Although Gregor Mendel demonstrated the principles of inheritance, Darwin was not aware of his studies…
[/QUOTE]

Not to detract from your otherwise excellent post, but Mendel didn’t publish his work until 1865, which was 6 years after Darwin published his famous work on evolution. And of course, Darwin had actually developed his ideas many years earlier, before Mendel even was Gregor. :slight_smile: