How Evolution Works

I have been asked many times to explain how so called “macro-evolution” works. There are of course many excellent books and articles online and off that cover this, but I thought it might be a good idea to have a blog post that explains it quickly and simply that I can refer to when asked. The following is adapted from a book manuscript (which might get published some day).

To see how macroevolution (the origin of new species) works, we can use a hypothetical animal, maybe one in the cat family. Let’s call it a lipard. And let’s say that there is a population of these large cat-like carnivores living on a large plain with plenty of prey animals. The lipards have gotten better and better at hunting thanks to several improvements (microevolution) in  vision, muscle strength, digestion of meat, and other traits. And all of these positive changes eventually got shared by the whole population of lipards, due to breeding and natural selection (like all examples of microevolution).

But now the population of lipards becomes divided so that there are two groups of lipards that cannot interbreed. Perhaps one group crossed a river, a desert, or a mountain range and couldn’t get back, or they just wandered so far away that it wasn’t convenient to find mates in the other group.

Now both groups of lipards continue to accumulate new genetic variations through mutations, but because they are no longer interbreeding with each other, the new variantions in one group do not spread to  the other group. With time, each group begins to differ in their variations. Now, for each  group, natural selection could choose different genetic variants to be successful than in the other group.

Its also possible that some differences in the two groups could arise by chance, and not have any important effects on survival (like slight differences in skin color). But the key point is that none of the changes will spread to the other group, because the two populations cannot interbreed.

With the passage of time,  different traits will appear  in one of the groups that are not found in the other. In one group, the skin could become darker, and in the other, males could develop a large mane of hair around their heads.  Both groups continue to change independently of each other, and after a long enough time, neither group resembles the original lipards. One group has become lions, and the other has become leopards.

They still have a lot in common, but they are now two separate species. Please note that no lion turned into a leopard or vice versa. Both lions and leopards share a common ancestral species, the lipard, which now no longer exists. It didn’t go extinct – it evolved. Lipards themselves had evolved from an ancestor that they had in common with tigers and snow leopards, and even further back with cheetahs and domestic cats. And they all became separate species the same way: population isolation, separate genetic changes in the separate populations, and continued evolution by natural selection. This is what Darwin observed among species of finches in separate islands of the Galapagos chain.

We can keep looking backwards in biological history. All the cat-like animals are descended from a no-longer-living ancestor shared with bears, wolves, hyenas, badgers, and other carnivores. If we keep going we will find a common ancestor for all mammals, and then all vertebrates, and so on. For an excellent book that describes all of this in beautiful detail, there is nothing to match The Ancestor’s Tale by Richard Dawkins.

Is there any evidence for this scenario of how the diversity of life arose? Yes, tons. There is so much evidence, both in fossil records and from genetics, that there is no doubt at all that the theory of evolution for the origin of species is correct (though perhaps not complete – see “New Ideas in Evolutionary Biology”).

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22 Responses to How Evolution Works

  1. Heather G says:

    Reblogged this on All Things are Yours.

  2. David says:

    Sy, you know that science is about what’s observable & repeatable. Where is the evidence for this ‘common ancestor’?
    There is none so it’s just an unprovable hypotheses. Don’t be suckered into accepting a view just because lots of people believe it. There’s got to be evidence or it’s not science but blind faith!

    Genesis says it all – the Lord made distinct species ‘after their kind’. Macro evolution is impossible* & no one has ever observed it. We make God too small & rob Him of His glory!

    eg a human knee has irreducible complexity – you need at least four co-dependent parts to be all present and in the perfect place at the same time.

  3. David, Welcome to the Book of Works, and thanks for your comment. Clearly we dont agree on evolution, but I posted this mostly for those who are interested in how evolution actually operates. I dont intend to get into a discussion on why evolution is correct (And in fact is a testament to God’s majestic creativity). You can find lots of good arguments at Meanwhile take a look around and see if anything else interests you here. As a scientist, I am mostly involved in God’s Book of Works (nature) and although I am slowly learning, my Biblical and theological knowledge is still less strong. Blessings

    • David says:

      Thanks for the reply Sy as I know you must be busy.

      I had a quick look at BioLogos. I don’t think they have the same high view of Scripture as Jesus! eg their view that the Flood was a localised event, which is not what Jesus, nor the apostles, stated. Their view also conflicts with the clear reading of Genesis as well as the evidence of geology. (Whole flood beds across N America with debris all pointing in the same direction – ie a massive catastrophic event.)

      Jesus confronted this sort of thinking when he said to the Saduccees (religious group of materialists), “Is not this why you are wrong, that you know neither the scriptures nor the power of God?” (Mark 12:24)

      God is not fooling around with us & gave His word so that we can be certain of the truth about who He is & what He’s done through the cross. The fate of millions depends on the certainty of this for salvation. We don’t have the luxury of picking & chosing which bits we’ll accept & believe.

      Thanks again.

  4. SheilaDeeth says:

    Thank you. Lovely post (and I love the Ancestor’s Tale). Seeing how evolution might work is like learning the sound of music instead of just reading the silent notes.

  5. Thanks, Sheila. Love the analogy.

  6. yellowyarrow says:

    I have never been too sure about ‘macro-evolution’ Yes, I do understand the comcept of natural selection and adaption, but do find the rest of it somewhat unclear.
    So, I would like to ask you a question. Does evolution mean (and going by your explanation) that potentially, in hundreds of thousands of years, maybe less, perhaps more, that human beings could change so much that we would no longer be humans. We may end up unrecognisable from what we now are? And what would that mean regarding God’s salvation of mankind (assuming He hasn’t ‘wrapped everything up’ by then as foretold in the Bible?

    • That’s a good question, and the answer is that if you think about it, humans have changed tremendously over the past 4000, 400, and even the past 4 years. But these changes were not due to biological evolution, (genetics) but because of cultural evolution, like technology and social changes. That includes learning to read and write the Bible, learning about God, and so on. Evolution is very slow, much slower than can be seen in humans, there are only a few examples of genetic evolution in human being in the past 50,000 years. One is changes in skin color as humans moved around the globe, and the other is the ability to drink milk after infancy. All the rest is cultural which comes from our brains, not our genes. So I think that we shouldnt worry much about evolution changing us beyond recognition. If we do, it will be because of some social, political or cultural reason. But I am hopeful that future humans will not be too different (but maybe better in many ways) than we are.

      • yellowyarrow says:

        OK, thanks for your reply…but nonetheless TECHNICALLY the, we or other animals COULD end up having six legs or two heads or horns or whatever really, if any mutations, genetic changes etc were able to be passed on successfully. I mean obviously, we are all totally different from the original one-celled creatures But, basically, over the millenia, animals and humans have hardly changed at all…they’ve basically been the same apart from minor differences, such as you pointed out.

      • David says:

        Good point. I’ve never heard anyone say how new information is added to the genetic code to give a viable, complex new structure. Small step changes cannot lead to a new, irreducably complex organ.

        So much of macro evolution seems to be based on unsubstantiated theory rather than evidence, per the scientific method.

        It almost looks like people fit hypotheses to a given philosophy, rather than following the actual evidence.

        Scientists apparently admit concerns about macro evolution in private, but only a few are willing to put their head above the parapet for fear of losing research grants, and loss of professional status.

  7. David

    Your last paragraph is not true. Research into how new information is added to existing creatures is a vibrant and exciting field of evolutionary biology. One pioneer, Andreas Wagner, has wriiten an excellent book on the subject for the non-specialist called “The Arrival of the Fittest”. Many papers and research grants are now devoted to understanding this important question.

    • yellowyarrow says:

      Bookofworks:- Do you know of any websites with information as to ‘arrival of the fittest’…as I cannot afford to buy books. I have never read anywhere anything about information being added per se, so would be interested to see what evidence there is of this.

  8. yellowyarrow says:

    David:- No, I’ve never seen anything about how new information can be added either

  9. Search for Andreas Wagner the Third Way of Evolution, and check out the resources on

  10. Excellent explanation, Sy. I especially like the humanity of your lipards.

  11. archicastor1 says:

    Loved your explanation, Sy. Thanks!

  12. resonate47 says:

    Great explanation Sy. Thank you for this. Biology is amazing.

  13. vicardwm says:

    The theory of evolution makes sense, Sy. However, it is my understanding that they have not found nearly as many transitional forms as they were expecting to find, which led to theories of “punctuated equilibrium”, which means that bursts of quick evolution took place, which explains the lack of transitional forms. If this is true, however, isn’t macroevolution more of a matter of faith?

    As far as genetic similarity, is this really a proof of evolution, or just evidence that God used the same basic design for His creatures? I am a strong Catholic who is agnostic on the theory of evolution, and am open to evidence one way or the other.

  14. quierofuego says:

    OK, here’s a few questions that come up for me…

    1) Aren’t genetic mutations nearly always detrimental and only beneficial in very rare cases? If so, it seems that a series of genetic mutations, even if it included some of the rare beneficial mutations, would still end up in extinction rather than a new and improved species. Even if 9 mutations were detrimental and one was beneficial, I imagine it would be very difficult to get an end result that was better.

    2) The question with some proposed “evolutionary stages” is “how does this animal survive at the intermediate stage?” One example is that of a bird’s lungs in the evolution from a reptile to a bird. At the intermediate stages, the animal would be unable to breathe properly and die, thus never making it to the bird stage. Questions like these must be answered. Here’s an explanation I just found of the bird problem in particular. Maybe you can respond to it with an explanation:

  15. I will answer your first question now, but I am in a very busy period, and will need to get back to your send question later. For the first question, you are right that most mutations are deleterious, and when they occur (say in a single cell) the cell might die or do more poorly. But the death of one cell has little effect on the overall population. By contrast a single beneficial mutation has a great impact. Consider this illustration:

    If we start with a population of a million cells growing on a dish and add a poison, they will all die. But if we first add a chemical that causes mutations, we find that many of the cells (say 10%) will develop mutations. The majority of those mutations will be harmful, and 90% of the mutated cells will die. That leaves 10,000 of the one million total cells in the dish with nonlethal mutations.
    Now we add the poison. All the cells with no mutations die. What about the 10,000 mutated cells? Almost all of them die also, because their mutations do nothing useful about the poison. But two of those 10,000 (0.02%) cells have a mutation that changes the way the cell transports or metabolizes or excretes the poison, and those two cells survive. And they reproduce. And after a few days, we don’t see an empty dish. We see a dish with two visible colonies of healthy, growing cells. Within a week or so, the dish is full of cells that have resisted the poison. This is not a thought experiment; most biologists including me have personally done such experiments.

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