Okay, what do we have here? Well, we do have something shared and derived. The primitive character state is a T. What's derived is this A, and its A is found in the in-group. And that's good, it's nice, it's kind of comforting, but we already knew that the in-group was a clade.
We defined that. We said that the in-group was a clade. clade.
By definition, by designating the rhesus as an out-group, we wanted to know the relationships within the in-group. So we, by definition, had already determined that the in-group was a clade. So this is good. It confirms that this is a clade, but it really doesn't answer the question that we set out to address.
So... This isn't phylogenetically useful as far as determining the relationships within the in-group, within the gibbon and the great apes and the human. Same thing here, that's a synapomorphy for the in-group but not helpful for the relationships within the in-group in position 18. Ah, now we're making some progress. Now here I'm going to use, from here on I'm going to use the red to show synapomorphies.
We have a synapomorphy here and I'm going to use the yellow and the black to show the primitive condition. So the primitive condition here is found in the rhesus monkey and it's shared in the gibbon, the orangutan, and the gorilla. And we have a synapomorphy for the human and...
The two chimps, and it's a mutation in the ancestor of the human and the two chimps mutated to a T, and so for position two, we have evidence supporting a relationship, a common ancestor, for those three species. Position seven, additional evidence supporting a human. Chimp clade, human and the two chimps.
And again, position 25, same thing. So here's what we have so far in our tree. We have three positions, position 2, 7, and 25, that support a relationship between the two species of chimps and a human. At this point, we don't know whether the The two chimps are more closely related to each other, or if the human is related, more closely related to one or the other of the chimps. As far as our data set goes, we haven't found anything that we've looked at so far that we've discussed that elucidates that.
But here we go. Let's look at position 9. And in red, you see a synapomorphy. The primitive state is A in the rhesus monkey.
You see four species, including the human, that share the primitive state, and there's a synapomorphy, a shared derived state in the two species of chimps, a G in the ancestor of the two chimps, and I put a 1 there indicating in the tree, one character where there's a synapomorphy showing evidence supporting a chimp. clade between the two species of chimps. Now, position 19, there's another one.
Now there's two. We have a primitive state of G and a derived state of C in position 19. Now in 16, this is a little more complicated. What's the primitive state? Primitive state is G. That primitive state is retained in the gibbon and in the human, but we do still see a synapomorph, a shared derived state in the two species of chimps.
A mutation to C in the common ancestor of the two chimps. We also have two autapomorphies. The gorilla went to T, the orangutan went to A. That doesn't change the fact that the two species of chimps are the same. that there's a synapomorphy in the two chimps.
So we still have evidence in those chimps that those that they shared a common ancestor. So now we have three nucleotide positions that support a relationship between the two chimps and three that support a relationship between the chimps and the human. Now here's position 15. Position 15 has a primitive state of C and we have a synapomorphy.
In red you see a A synapomorphy for human, chimp, and gorilla. And I put that on the tree. We have one synapomorphy for the human chimp gorilla clade.
Now look ahead. Do you see any more synapomorphies for a human chimp gorilla clade? There it is. Position 21. There's our... Other human chimp gorilla clades, so there's two of them.
Now here in position 11 is a human chimp orangutan synapomorphy. Primitive state is T and a derived shared state of C in the human chimp gorilla and orangutan. Looks like another one in 17 and yet another one in 24. There's 17 and there's 24. So there's three that support a human chimp and orangutan.
Now by definition we know the out group goes at the root of the tree. We said that at the beginning. We said that this old-world monkey falls outside of the human and ape clade. Now what about position 10? In position 10, the primitive state is a T, thiamine, and that is shared in the gibbon, the gorilla, and the two chimps.
But we have a shared derived state, a synapomorphy, between the human and the orangutan. Does this provide evidence for a human orangutan clade? And the answer is, yes it does.
Do we have a human orangutan clade in our tree? So what do we have here? Well, you know the answer to that already from our previous lecture.
What we have here is a homoplasy. This is most reasonably explained by saying that the similarity in position 10 between a human and orangutan, this G, is a result of a independent mutation that arose in the human and the orangutan separately, rather than something that developed in a hypothetical common ancestor between the human and the orangutan. If we were to suggest a human orangutan clade supported by this one nucleotide position, then we would have to look at all of the other evidence and we would find a tree that has many many homoplases.
For example, remember all these positions that supported a human chimp clade. We would have to say that all of these positions arose independently. in two different lineages and all of the other positions that we discussed arose independently in separate lineages and we would have a less parsimonious tree.
Now in a real data set we would have hundreds even thousands of DNA nucleotide positions. You'll see there's a gap here, they're not showing all the DNA but this is position 3903 and We're going up all the way up to 8,474, so there's literally thousands of DNA positions, and we can look at several different genes, so we can look at lots and lots of data, and we're looking at sometimes hundreds of synapomorphies that support the various branches on the tree. And the more DNA positions that we look at, the more confidence that we can have in the phylogeny that we develop.