Conceptualizing evolution: microevolution, macroevolution, and the fossil record

Pete Harcoff · #1 2nd March 2004, 07:22 PM

One of the roadblocks in discussing evolution with people is getting them to conceptualize the process. People are used to visualizing things relative to their own lives. It's easy to conceptualize how long a week or month or year is. But try imaging a thousand years. Or ten thousand. Or a million. It's pretty much impossible, because we're just no used to dealing with such vast periods of time in our own lives.

Likewise, the same problem occurs with evolution. People are used to seeing animals give birth to the same kinds of animals. Dogs give birth to dogs. Humans give birth to humans. Creationists seize on this to create misconceptions about evolution, like "monkeys give birth to monkeys, not humans" or "when has a dog ever given birth to a non-dog?". They are creating a misconception based on the way we see every thing today. We see modern dogs, modern apes, modern humans, and it's difficult to see how such species could be related by common ancestry.

The first thing to understand is that there is no magical process for change in biological evolution. The minor variations we see in organisms today is part of the same process that diversified all life. Sure, we see dogs giving birth to dogs, cats giving birth to cats. But dogs give birth to slightly different dogs, which then give birth to slightly different dogs, and so on and so on, until you wind up with something we might no longer call a "dog". But there is no magic moment when a dog suddenly gave birth to a non-dog in a single step. The actual change is relatively gradual.

Diagram 1: Microevolution and Macroevolution

To conceptualize this process of change, see the above diagram. In it, the color orange gradually becomes the colour yellow. The overall change is clearly visible. But if you zoom into a point along the bar, the change becomes much less apparent. The section I zoomed in on looks uniform orange, yet there is actually a tiny change from the left side to the right side (note: because it's a GIF file limited to 256 colors, the color might actually be uniform; but in the original Photoshop version there was a slight difference). The difference, of course, is almost imperceptible. It's like seeing dogs producing dogs. We just don't see the dramatic level of change the overall picture provides. And with respect to biological evolution, the overall picture is far greater than human lifespans or even human civilization.

Diagram 2: Rates of Change

The previous picture showed a pretty linear picture with a constant rate of change. The reality of biological evolution is that rates of change vary. In the above picture the gradation is more dynamic. But even during "rapid" periods of change, the changes are still difficult to detect when zoomed in to a specific spot.

Diagram 3: Branching Evolution

Another factor is that evolution is not a linear path from Species A --> Species B --> Species C --> etc. Evolution is a branching tree. Populations split and diversify, then those new populations further split and diversify, etc. The resulting picture is much more complex. But again, if you zoom into any point on the tree you wind up with the same barely perceptible rates of change. Dogs producing dogs, as it were.

Diagram 4: Discontinuity in the Fossil Record

The problem with historical development of species is we don't have an exact record of every single organism or even every single species that ever lived. Fossilization is an extremely rare process in itself, not mention actually finding the fossils. Yet, even with the fossils that are found it is possible to big putting together these branching patterns of the historical development of life. Granted, scientists doing this may make mistakes, but as more fossils are found, a clearer picture forms.

Diagram 5: Fossil Hominid Skulls

Even with the fragmentary picture formed from the fossil record, patterns do emerge. Pictured above are a series of fossil skulls (adapted from a picture at Talk.Origins). When arranged chronologically, there is a clear pattern of evolutionary development. Keep in mind that the actual evolutionary development was probably not linear, and followed a branching pattern similar to the previous two diagrams. This does not change the fact that there is a pattern of gradual evolutionary change with respect to the chronology of the fossils.

I hope that this might help some people who have trouble conceptualizing the process of biological evolution. It can be difficult to visualize, especially if one is just used to seeing everything as we see things today, relative to our own lives. But there is a bigger picture out there. It just takes a little work to see it.

(If anyone can see any points that need correction or things that should clarified or explained differently, let me know.)

rihu76 · #2 2nd March 2004, 08:49 PM

Originally Posted by Pete Harcoff

But dogs give birth to slightly different dogs, which then give birth to slightly different dogs, and so on and so on, until you wind up with something we might no longer call a "dog". But there is no magic moment when a dog suddenly gave birth to a non-dog in a single step. The actual change is relatively gradual.

Yes, our naming conventions are abstract labels we place on organisms. In reality, these categories and labels do not exist. Everything is continuous.

Good post Pete. Very comprehensive.

gluadys · #3 3rd March 2004, 01:25 AM

Excellent post.

Another conceptualization problem stems from the fact that most people can name very few animals (mostly mammals) and even fewer plants or fungi. Most think of unicellular life as one amorphous mass and don't even distinguish between eucarya, bacteria and viruses.

As a consequence they tend to think of all common terms as referring to species i.e. as being at the same taxonomic level.

This is rarely the case. Among mammals the only common names I can think of that refer to a single species are "playtpus" and "human".

"rhinoceros" refers to a genus with two distinct species.

A great many common terms refer to animal families rather than to a species or genus. Some examples would be "rabbit", "beaver" and even "armadillo". (Would you guess there are several separate genera of armadillos?)

Then there are terms like "spider", "frog" and "bat" which refer to whole orders. These are not species or even a small closely related group like a genus. They are on a par with terms like "carnivore" and "rodent".

If one is accustomed to thinking of the various types of frogs as being related to each other on the same level as various breeds of domestic dog, then no wonder it seems ridiculous to hear that a cat and a bear are more closely related to each other than two different species of frogs.

But in fact, since frogs are actually an order, and have been in existence much longer than all mammals, the range of diversity among frogs is much greater than among all mammals put together.

And then there is the lowly worm--a designation given indiscriminately to several different phyla. I am sure most creationists cannot grasp the idea that some worms are much more closely related to humans than they are to other worms.

Cantuar · #4 3rd March 2004, 04:17 PM

Pete, are those pictures of yours all separate or is there a way to get to the overall Evolution page on that site of yours?

PhantomLlama · #5 3rd March 2004, 04:25 PM

Originally Posted by gluadys

But in fact, since frogs are actually an order, and have been in existence much longer than all mammals, the range of diversity among frogs is much greater than among all mammals put together.

It's even worse when they say it about bacteria, seemingly without realising that there is more diversity among bacteria than the entire multicellular kingdoms combined.

Pete Harcoff · #6 3rd March 2004, 05:23 PM

Originally Posted by Cantuar

Pete, are those pictures of yours all separate or is there a way to get to the overall Evolution page on that site of yours?

The pics are seperate and were created just for this post. I don't have a seperate evolution page (yet).

Faithful83 · #7 3rd March 2004, 06:22 PM

Likewise, the same problem occurs with evolution. People are used to seeing animals give birth to the same kinds of animals. Dogs give birth to dogs. Humans give birth to humans. Creationists seize on this to create misconceptions about evolution, like "monkeys give birth to monkeys, not humans" or "when has a dog ever given birth to a non-dog?". They are creating a misconception based on the way we see every thing today. We see modern dogs, modern apes, modern humans, and it's difficult to see how such species could be related by common ancestry.

Please explain how this creates a misconception? It wouldn't surprise me if what we see today can tell us a lot.

Sure, we see dogs giving birth to dogs, cats giving birth to cats. But dogs give birth to slightly different dogs, which then give birth to slightly different dogs, and so on and so on, until you wind up with something we might no longer call a "dog". But there is no magic moment when a dog suddenly gave birth to a non-dog in a single step. The actual change is relatively gradual.

Dogs have been called dogs even in the Bible, which was, whether you believe in young earth or old earth, a loooooooong time. We have yet to see something that we would not call a "dog."

Faithful83 · #8 3rd March 2004, 06:24 PM

By the way, I would like to take this moment to say, while we're talking dogs here:

I do believe in creation rather than evolution. I do believe that God created the wolf. Am I denying that the dog came from the wolf? No, but man domesticated the wolf and bred it and bred it until it became a dog. If any type of evolution exists, it's man-made evolution (aka selective breeding), not evolution that just happened in place of creation.

napajohn · #9 3rd March 2004, 06:35 PM

Originally Posted by Pete Harcoff

One of the roadblocks in discussing evolution with people is getting them to conceptualize the process. People are used to visualizing things relative to their own lives. It's easy to conceptualize how long a week or month or year is. But try imaging a thousand years. Or ten thousand. Or a million. It's pretty much impossible, because we're just no used to dealing with such vast periods of time in our own lives.

Likewise, the same problem occurs with evolution. People are used to seeing animals give birth to the same kinds of animals. Dogs give birth to dogs. Humans give birth to humans. Creationists seize on this to create misconceptions about evolution, like "monkeys give birth to monkeys, not humans" or "when has a dog ever given birth to a non-dog?". They are creating a misconception based on the way we see every thing today. We see modern dogs, modern apes, modern humans, and it's difficult to see how such species could be related by common ancestry.

The first thing to understand is that there is no magical process for change in biological evolution. The minor variations we see in organisms today is part of the same process that diversified all life. Sure, we see dogs giving birth to dogs, cats giving birth to cats. But dogs give birth to slightly different dogs, which then give birth to slightly different dogs, and so on and so on, until you wind up with something we might no longer call a "dog". But there is no magic moment when a dog suddenly gave birth to a non-dog in a single step. The actual change is relatively gradual.

Diagram 1: Microevolution and Macroevolution

To conceptualize this process of change, see the above diagram. In it, the color orange gradually becomes the colour yellow. The overall change is clearly visible. But if you zoom into a point along the bar, the change becomes much less apparent. The section I zoomed in on looks uniform orange, yet there is actually a tiny change from the left side to the right side (note: because it's a GIF file limited to 256 colors, the color might actually be uniform; but in the original Photoshop version there was a slight difference). The difference, of course, is almost imperceptible. It's like seeing dogs producing dogs. We just don't see the dramatic level of change the overall picture provides. And with respect to biological evolution, the overall picture is far greater than human lifespans or even human civilization.

Diagram 2: Rates of Change

The previous picture showed a pretty linear picture with a constant rate of change. The reality of biological evolution is that rates of change vary. In the above picture the gradation is more dynamic. But even during "rapid" periods of change, the changes are still difficult to detect when zoomed in to a specific spot.

Diagram 3: Branching Evolution

Another factor is that evolution is not a linear path from Species A --> Species B --> Species C --> etc. Evolution is a branching tree. Populations split and diversify, then those new populations further split and diversify, etc. The resulting picture is much more complex. But again, if you zoom into any point on the tree you wind up with the same barely perceptible rates of change. Dogs producing dogs, as it were.

Diagram 4: Discontinuity in the Fossil Record

The problem with historical development of species is we don't have an exact record of every single organism or even every single species that ever lived. Fossilization is an extremely rare process in itself, not mention actually finding the fossils. Yet, even with the fossils that are found it is possible to big putting together these branching patterns of the historical development of life. Granted, scientists doing this may make mistakes, but as more fossils are found, a clearer picture forms.

Diagram 5: Fossil Hominid Skulls

Even with the fragmentary picture formed from the fossil record, patterns do emerge. Pictured above are a series of fossil skulls (adapted from a picture at Talk.Origins). When arranged chronologically, there is a clear pattern of evolutionary development. Keep in mind that the actual evolutionary development was probably not linear, and followed a branching pattern similar to the previous two diagrams. This does not change the fact that there is a pattern of gradual evolutionary change with respect to the chronology of the fossils.

I hope that this might help some people who have trouble conceptualizing the process of biological evolution. It can be difficult to visualize, especially if one is just used to seeing everything as we see things today, relative to our own lives. But there is a bigger picture out there. It just takes a little work to see it.

(If anyone can see any points that need correction or things that should clarified or explained differently, let me know.)

its NOT a concepualization problem but a problem not supported by the fossil record..Your story would work if you can find the animals turning from one species to another as you claim...since its gradual.. you should see thousands of species in transition in the fossil record..so where are they in spite of the storytelling?

Arikay · #10 3rd March 2004, 06:49 PM

Thats not a long time, less than 5000 years I believe, which is pretty short for the change of magnitude that many creationists want (which is ironic, since often creationists rely on hyperevolution to make things fit).

We have, however, seen one species become another species. Evolution happens in small steps (especially when compared to the life span of a human, or even the oldest civilization).

Originally Posted by Faithful83

Please explain how this creates a misconception? It wouldn't surprise me if what we see today can tell us a lot.

Dogs have been called dogs even in the Bible, which was, whether you believe in young earth or old earth, a loooooooong time. We have yet to see something that we would not call a "dog."