Human Evolution

[Jose]

jcrawford and I have been having some interesting discussions in other threads, which have led to the notion that we really need a thread on human evolution. So, here it is.

The Rules
We want to work from data. Data that is discussed must be accessible in the scientific literature. Personally, I would prefer the peer-reviewed literature, because, as those of us in science know all too well, the peer reviewers are usually one's competitors. Thus, they are typically extremely critical of what we write.

Any other information that is brought to bear must also be accessible to everyone. Where requested, direct quotes from the sources will be important.

The questions for discussion

1. What is the current best understanding of human origins?

2. What "confounds" are there in the interpretation of data?

3. Given that there is always genetic diversity within populations, how easily can we assign hominid fossils to different groups? Here, the term "form-species" is probably most useful, referring to similar fossils with similar forms, but in the absence of information on the capacity for interbreeding. In many cases, different form-species are different species (fossil trees vs fossil insects), but sometimes they are not (fossil leaves vs fossil roots of the same tree).

4. Does information based on fossil data mesh with information based on genetic data? The true history must be genetically feasible. The fossils must have been left by individuals who were produced by normal genetic methods. To be valid, any explanation of origins must incorporate both fossil and genetic data.

5. What are the parts of human history that are most at odds with (some) Christian views, and what suggestions can we offer for reaching a reconciliation?

I will begin by posting the following genetic data, which is pictorial representation of the differences and similarities in mitochondrial DNA sequence of a whole bunch of people. Relative difference/similarity is proportional to the lengths of the vertical lines. Horizontal lines merely separate the vertical lines so we can see them.

How do we interpret these data?

[If appropriate, I will edit this post to ensure that the OP of this thread lists the important questions.

[jcrawford]

What I described concerning the acquisition of mutations in a population is simply the only way that it can happen and remain consistent with the chemistry and biology. If that scenario happens to match "neo-Darwinist logic," why, then I'd have to conclude that maybe their logic might be OK.

There's nothing wrong with neo-Darwinist logic, Jose. It is quite precise and scientific. The problem is that neo-Darwinist pre-supposititions, assumptions and premises about the ancestral origins of racial groups are racist.

In these cases we would be using members of the same species (Crawford and Jose) as outgroups, so it's not similar to using a chimp at all. Using a chimp as the outcrop influences the genetic data in the diagram.

It turns out that it actuall is quite similar. In fact, we'd get the identical result for the jcrawford and Jose trees using chimp DNA as the outgroup as we would if we used each other, or if we used Bill Clinton for the outgroup. I've prepared a little figure to make this more clear:
[/quote]

There you go again. Blowing the data on the screen into extra dimensions so that we have to slip and slide left to right and back again just to read the screen. I know you didn't do it on purpose, Jose, but would you mind re-adjusting the diagram proportions to normal screen size like you did for us with your previous diagram? Thanks. You're a real champ in my book, whether you win this debate or not.

[Jose]

Your logic was based on typical neo-Darwinist theory though. Just like Darwin used original biblical concepts and ideas of the common ancestral origins of human beings in his own speculations on the origin of species from a common ancestor.

If the result is similar, it may seem possible to have done the logic backwards. I started with genetics, and let the facts lead where they might.

This is rather an excellent point on your part, Jose, since we are both obviously operating on two different wave lengths or in different worlds or paradigms, to say the least. You see, I don't accept the neo-Darwinist paradigm at all, including the division and classification of ancestral racial groups into separate 'species' or the dating techniques used to establish the age of any human fossil.

That's cool. The key here is that we don't care who accepts what theories or logic. We start with the data.

But back to the question: why should it matter if two species are contemporaneous?

Your logic was based on typical neo-Darwinist theory though. Just like Darwin used original biblical concepts and ideas of the common ancestral origins of human beings in his own speculations on the origin of species from a common ancestor.

Again, you're presupposing the logic based on the result. I freely admit that I cannot divorce myself from the genetic and embryological facts with which I am intimately familiar, and try to construct an explanation that does not take them into account.

What Darwin's logic was is not germane to this discussion, fun though it may be. We're starting with the data.

[jcrawford]

Your logic was based on typical neo-Darwinist theory though. Just like Darwin used original biblical concepts and ideas of the common ancestral origins of human beings in his own speculations on the origin of species from a common ancestor.

If the result is similar, it may seem possible to have done the logic backwards. I started with genetics, and let the facts lead where they might.

Thanks for re-adjusting the screen for us Jose. You really are a champ. Funny how the word champ is just one vowel different than chimp. Sort of like the 95% approximation of the chimp genome to human.

You say you start with human genes but include the chimp genome in your sample diagram. How would the diagram look if you excluded the chimp as a relevent outcrop?

This is rather an excellent point on your part, Jose, since we are both obviously operating on two different wave lengths or in different worlds or paradigms, to say the least. You see, I don't accept the neo-Darwinist paradigm at all, including the division and classification of ancestral racial groups into separate 'species' or the dating techniques used to establish the age of any human fossil.

That's cool. The key here is that we don't care who accepts what theories or logic. We start with the data.

Yes, but what exactly is the data which you are presenting as evidence of human evolution? I don't see any evidence of evolution in the diagrams that you have presented so far.

But back to the question: why should it matter if two species are contemporaneous?

According to neo-Darwinist theory, two human species cannot exist on earth today because one will out-populate, out-produce, and drive the other into extinction according to the natural laws of superior adaptation and selection.

Your logic was based on typical neo-Darwinist theory though. Just like Darwin used original biblical concepts and ideas of the common ancestral origins of human beings in his own speculations on the origin of species from a common ancestor.

Again, you're presupposing the logic based on the result. I freely admit that I cannot divorce myself from the genetic and embryological facts with which I am intimately familiar, and try to construct an explanation that does not take them into account.

What embryological facts are you referring to here, Jose?

What Darwin's logic was is not germane to this discussion, fun though it may be. We're starting with the data.

There is no raw data, Jose. All interpretations and facts based on data are the result of theoretical pre-suppostions and assumptions about them, as pointed out by Karl Popper and Einstein himself.

Show me some "data" that indicates that today's human beings evolved from other 'species' of human beings who in turn evolved from African monkey and ape ancestors once upon a time.

You can use neo-Darwnist notions of genetic mutation, adaptation and natural selection if you care to, but you're still going to fall into the inescapable trap of racism once you arrive at that evolutionist point in pre-history where there are no other human beings on earth except those first few African people whom Darwin imagined to have closely resembled African ape and monkey ancestors in their earliest stages.

[jcrawford]

In these cases we would be using members of the same species (Crawford and Jose) as outgroups, so it's not similar to using a chimp at all. Using a chimp as the outcrop influences the genetic data in the diagram.

It turns out that it actuall is quite similar. In fact, we'd get the identical result for the jcrawford and Jose trees using chimp DNA as the outgroup as we would if we used each other, or if we used Bill Clinton for the outgroup. I've prepared a little figure to make this more clear:

Now the diagram is too small to be ledgible. Nevertheless, may we substitute Bill Clinton for the chimp and assume that the diagram will remain unchanged? Assuming so, what does the diagram now tell us about the evolution of such racial groups as are indicated in your previous diagram?

[Cathar1950]

First it is to big then it is to little.
Why does chimp have such a small geneology line?

[Jose]

Thanks for re-adjusting the screen for us Jose. You really are a champ. Funny how the word champ is just one vowel different than chimp. Sort of like the 95% approximation of the chimp genome to human.

You say you start with human genes but include the chimp genome in your sample diagram. How would the diagram look if you excluded the chimp as a relevent outcrop?

I have now re-saved some of the illustrations at alternate sizes, in hopes that they will be neither too large nor too small. Keep me posted.

Your question is a good one. I have two kinds of answers. First, consider the words, privet, civic, livid, umpire, implode, hammer, topping, and steeple. How are they related? Suppose I tell you that I got them by slight changes from one word to another. Where did I start? Even if I give you all of the words, you can't figure out where I started. You could relate the words to each other, but you'd have an "unrooted tree."

However, I can provide a root for the tree by giving you another word that is related to the words with which I started. Then, the tree is this:

You're quite right. Chimp and champ are pretty similar, as is chump.

To answer your question more directly, if we don't have a "root" for the human tree, we could still draw the tree the same way (top figure below), but I'm not sure we'd have confidence that the base of it should be where it is. More accurately, we'd need an "unrooted tree" like that shown in the lower panel.

uhhh...is this too small? I've tried to adjust it, but my browser is too busy remembering the small one and won't update itself!
From the unrooted tree, we don't have any good way of determining where to start (i.e. where the oldest ancestor might be), but we nonetheless see that there is more, and much "deeper" diversity among Africans than among non-Africans. We still see that there are several main branches to the tree, and that non-Africans are all on one such branch along with one of the African groups. The pattern of relationships is unchanged.

Of course, without the root, we have no basis for suggesting that there is genetic evidence that could help us answer the question of who our nearest relatives might be. Nor can we answer the question of how humans are related to all other species. For that, we need comparisons among species, not just within a single species.

We can examine those kinds of comparisons later, after we deal with this much simpler collection of data.

Yes, but what exactly is the data which you are presenting as evidence of human evolution? I don't see any evidence of evolution in the diagrams that you have presented so far.

Well, I'll suggest we follow our rules here. The diagram is a representation of the similarities and differences among a bunch of humans. The information is from DNA sequences, which are passed from parents to offspring, and which are subject to occasional mutation. The simple question, for which I seek your answer, is How do you explain how this pattern of relationships came to be? Describe for us a scenario that would produce this result, and that is biologically possible (you know--DNA passed from parents to offspring).

According to neo-Darwinist theory, two human species cannot exist on earth today because one will out-populate, out-produce, and drive the other into extinction according to the natural laws of superior adaptation and selection.

Unfortunately, there's no clear statement of "neo-Darwinist theory," so I can't ask you to prove that said theory actually states that. However, I suggest that this is a misconception. There is no rule at all about one species out-populating another. Why should there be? If a species that is well-adapted to living in grasslands has a small group--let's call it a tribe--that migrates off into a different place, and over a few centuries becomes adapted to living in mountains, then won't we have two different groups? One will live happily in the mountains, the other will live happily in the grasslands. If they aren't competing for the same resources in the same place, shouldn't they be able to co-exist?

What if the group that wanders off ends up on an island, or goes to a different continent. If the "new" species that they become is in a different place from the "old" species that their ancestors were, shouldn't the two different groups, in two different places, be able to live at the same time? Is there some magic process by which the diversification of one group on one continent somehow makes another group on another continent all fall over dead?

What embryological facts are you referring to here, Jose?

In the last 30 years or so, we've learned a tremendous amount about the genetic control of embryology. Ed Lewis was one of the pioneers in this, and pretty much provided the conceptual background for Iani Nusslein-Volhard and Eric Wieschaus to do their "saturation screen" for mutations that interfere with the establishment of the body plan in Drosophila. The three of them shared the Nobel prize for this.

From their analysis of flies, we developed the basic paradigm that is now the fundamental underpinning of embryological research: identifying the genes that control specific processes of cell-cell communication, establishment of "patterns," and control of other genes. Because most of these genes are highly conserved evolutionarily, their work with flies is directly applicable to human embryology and medicine, because we use the same genes. We don't grow wings, of course, because there isn't a "wing gene," but we do control many fundamental aspects of development the same way.

To simplify this, the "embryological facts" are that genes control development, and that changes in the expression of "developmental control genes" cause changes in physical characteristics.

There is no raw data, Jose. All interpretations and facts based on data are the result of theoretical pre-suppostions and assumptions about them, as pointed out by Karl Popper and Einstein himself.

You've lost me here. If "there is no raw data," then how can there be interpretations "based on data"?

Show me some "data" that indicates that today's human beings evolved from other 'species' of human beings who in turn evolved from African monkey and ape ancestors once upon a time.

We'll get there, don't worry. How about going one step at a time? Speaking of which, can you give me your interpretation of the diagram I've posted for you?

You can use neo-Darwnist notions of genetic mutation, adaptation and natural selection if you care to, but you're still going to fall into the inescapable trap of racism once you arrive at that evolutionist point in pre-history where there are no other human beings on earth except those first few African people whom Darwin imagined to have closely resembled African ape and monkey ancestors in their earliest stages.

I think we'll have to wait and see whether the data force us to that conclusion or not.

Why does chimp have such a small geneology line?

They used only one chimp sequence. I'd be interested in seeing a tree that has 100 chimps and 100 humans...There would probably be a human "bush" on one side, and a chimp "bush" on the other side, with the two family bushes joined by the branches of the tree. But, with only one individual, we don't get much of a tree.

[jcrawford]

To answer your question more directly, if we don't have a "root" for the human tree, we could still draw the tree the same way (top figure below), but I'm not sure we'd have confidence that the base of it should be where it is. More accurately, we'd need an "unrooted tree" like that shown in the lower panel.

uhhh...is this too small? I've tried to adjust it, but my browser is too busy remembering the small one and won't update itself!

The diagram sizes are acceptable even though they don't show the different racial groups evolving from common ancestors in Africa. We already know that there is genetic diversity in racial groups.

From the unrooted tree, we don't have any good way of determining where to start (i.e. where the oldest ancestor might be), but we nonetheless see that there is more, and much "deeper" diversity among Africans than among non-Africans. We still see that there are several main branches to the tree, and that non-Africans are all on one such branch along with one of the African groups. The pattern of relationships is unchanged.

Of course, without the root, we have no basis for suggesting that there is genetic evidence that could help us answer the question of who our nearest relatives might be. Nor can we answer the question of how humans are related to all other species. For that, we need comparisons among species, not just within a single species.

We can examine those kinds of comparisons later, after we deal with this much simpler collection of data.

Yes, but what exactly is the data which you are presenting as evidence of human evolution? I don't see any evidence of evolution in the diagrams that you have presented so far.

Well, I'll suggest we follow our rules here. The diagram is a representation of the similarities and differences among a bunch of humans.

Among various racial groups would be a little more scientifically precise. A bunch of bananas would be appropriate if we were dealing with genetic variety in that species.

The simple question, for which I seek your answer, is How do you explain how this pattern of relationships came to be? Describe for us a scenario that would produce this result, and that is biologically possible (you know--DNA passed from parents to offspring).

Jose, I'm a fossil man and am awaiting your explanation of the above.

[jcrawford]

According to neo-Darwinist theory, two human species cannot exist on earth today because one will out-populate, out-produce, and drive the other into extinction according to the natural laws of superior adaptation and selection.

Unfortunately, there's no clear statement of "neo-Darwinist theory," so I can't ask you to prove that said theory actually states that. However, I suggest that this is a misconception. There is no rule at all about one species out-populating another. Why should there be?

Here's a clear-cut neo-Darwinist rule of evolution that obviously applies to humans: The risk of extinction to a human species is proportionally increased to the degree that another human species continues to out-populate the first, in territorial expansion.

If a species that is well-adapted to living in grasslands has a small group--let's call it a tribe--that migrates off into a different place, and over a few centuries becomes adapted to living in mountains, then won't we have two different groups?

Not for long, according to the African Eve Model.

One will live happily in the mountains, the other will live happily in the grasslands. If they aren't competing for the same resources in the same place, shouldn't they be able to co-exist?

That would be nice, Jose, but you know how evolution works. A few individuals in one group or the other eventually mutate, migrate into the other's territory and are naturally selected to out-populate and dominate the other group.

[Jose]

The diagram sizes are acceptable even though they don't show the different racial groups evolving from common ancestors in Africa. We already know that there is genetic diversity in racial groups.

At least the diagram size is OK, for once! Now, to be "picky" about terminology, we can't show the groups evolving because that would require some kind of movie of the dynamic process. All we have are static timepoints. The current timepoint can give us data on lots and lots of individuals; fossils are each a single timepoint represented by a single individual. We need to put these different timepoints together to reconstruct the movie. In reconstructing the movie, we are constrained to ensure that the movie reflects genetic mechanisms accurately.

Among various racial groups would be a little more scientifically precise. A bunch of bananas would be appropriate if we were dealing with genetic variety in that species.

Again, to quibble with words: "a bunch of bananas" is a cluster of fruits all derived from a single tree. Not being the product of egg/pollen fertilization, but being the fruit tissue, all of the bananas are genetically the same within a bunch. But back to the issue at hand....

I disagree. The data are comparisons among a whole lot of individual humans. From the data we should be able to determine which groups represent different races, since "race" should be (and is, for other species) determined by genetic differences. A cluster of individuals that are relatively-closely related might be one "race." If you look at the diagram (especially the lower one, that has 4 groups rotated to different angles) you will see that we could view the data as 4 such clusters. The "genetic structure" of the human population thus seems to suggest that there might be 4 races. Given the locations in which these individuals live, we'd conclude that 3 of these races are strictly African, while the fourth includes some Africans plus everyone else.

There is no indication anywhere here that any of these races might be "superior" to any others. Nor is there any indication that the whole species of H. sapiens might be "superior" to any other species. The data merely indicate the genetic structure of the population.

Nor, I might add, is there any indication that there is any validity to the common notions of different races. The common notion is that skin color is what defines race. So, people tend to think of Africans as one race, Europeans as another, Asians as another, etc. This turns out not to be supported by the data. Rather, it is as you have said: there is genetic diversity. The one race that is comprised of Africans and non-Africans has genetic diversity, including diversity for skin color, hair color, and eye color. There is no justification for using any of these colors to define "race."

Jose, I'm a fossil man and am awaiting your explanation of the above.

This sounds somewhat evasive. Are you sure you don't want to give it a go? Or are you worried that you will find yourself saying things that, said by someone else, you would call "neo-Darwinist"? Tell you what: here's what micatala suggested:

even though the African population is restricted to a smaller geographic region, they have larger differences in their DNA sequences. Since DNA is passed down through inheritance, this means to me that more mutations must have taken place within the African population, or more generations producing more genetic differences through sexual reproduction.

It sounds rather like he is suggesting that the data indicate that African populations are older than other populations. It also seems necessary to conclude that the predecessors of the non-African populations were within one of these older populations. After all, their DNA had to come from somewhere, and the only links we find to other individuals' DNA are links to these older populations. The links to other species are less "tight" than the links to these other humans (although that isn't shown in the diagram, except by the one non-human datapoint labeled "C"). This suggests that the non-African populations are more closely related to other humans than to other species.

[jcrawford]

What if the group that wanders off ends up on an island, or goes to a different continent. If the "new" species that they become is in a different place from the "old" species that their ancestors were, shouldn't the two different groups, in two different places, be able to live at the same time?

For awhile. Eventually though, the "new" species either accidently becomes extinct and causes no further problems for the ancestors, the two groups remain isolated forever and there is no further evolution, or the "new" species becomes wildly successful in terms of it's sexual reproduction, cultural/technical innovation and territorial expansion, which causes some of its members to genetically drift back to the old continent to compete with the less-skilled and inferior ancestral species they originally left behind there.

Is there some magic process by which the diversification of one group on one continent somehow makes another group on another continent all fall over dead?

That's what I'd like to know since that is precisely the scenario presented by the African Eve Model. Some mythical Homo sapiens magically migrated out of Africa some one hundred tya, and poof, all other 'species' and racial groups around the world mysteriously disappeared into extinction.

No matter how one plays the game, Jose, neo-Darwinist theories of human evolution out of Africa are intrinsically and inescapably racist.