Whale Evolution: Theory, Prediction and Converging Lines of Evidence


(system) #1

This is a companion discussion topic for the original entry at https://biologos.org/blogs/dennis-venema-letters-to-the-duchess/understanding-evolution-theory-prediction-and-evidence-1

(George Brooks) #2

Great discussion … brings a whale-load of drama to something as miraculous as whale anatomy!!!

Great couple of paragraphs!

Independent Lines of Evidence, but Contradictory Stories?
Some of the genes known to be used in all mammals for tooth formation were the obvious candidate genes to start with: the products of the ameloblastin, amelogenin, and enamelin genes are all used in the formation of tooth enamel, the hardest structure in the vertebrate skeleton. Researchers went looking for these genes in several Mysticete (i.e. toothless whale) species. The results showed that all the species studied did indeed have these three genes present as pseudogenes (and more specifically, as unitary pseudogenes, a special class of pseudogene we have discussed in detail previously).

Finding these genes as pseudogenes in toothless whales was exactly what evolution predicted, but there was a catch: none of the mutations that removed the functions of these three genes were shared between different species, suggesting that these genes lost their function independently in the species studied. This finding was at odds with data from the fossil record, which suggested that teeth were lost only once, and early in the lineage leading to all modern toothless whales. So, the researchers seemed to have two lines of evidence that at face value contradicted each other. The fossil record suggested that tooth loss occurred once in the common ancestor of all toothless whales, but these three genes seemed to have been inactivated independently, several times over, suggesting that loss of teeth should be happening later in Mysticete evolution, and more than once.

One proposed explanation for the apparent discrepancy (among several put forward) was to predict that a fourth gene required for enamel formation was lost early in Mysticete evolution. The loss of any one gene necessary for forming enamel would be enough to prevent the process altogether. In this case, the loss of this fourth gene would prevent tooth enamel from forming, even though the genetic sequences of the other three enamel genes would still be intact. Once enamel function was lost, random mutations in the remaining enamel genes could then accumulate later in Mysticete evolution after speciation in this group was already underway. To test this hypothesis, the research group went hunting for other enamel genes in toothless whales.
[END OF SECTION]


Creating Information Naturally, Part 1: Snowflakes, Chess, and DNA
(Branko Miletich) #3

This is not a scientific discourse on whale evolution, but rather an embarrassment with some of the assertions made. The most obvious is the “Ontogeny recapitulates phylogeny” argument which any serious scientist would have identified in the article.

Apologies, but any reference to whales evolving without an objective view of the evidence is damming. This website lost my respect & confidence after just one article.


(Christy Hemphill) #4

Recapitulation theory was wrong because it posited a unifying law for all embryo development, and because it suggested that change in organisms happened because environmental forces worked on the embryo. Nothing like that is assumed or advocated in this article. On the other hand, evolutionary developmental biologoy (evo-devo), which studies homology in embryonic development between organisms to infer ancestral relationships(the topic actually discussed in this article) is a current and productive field of biological research. So this seems like a pretty spurious objection.


(Phil) #5

Do you have any specific criticisms or topics you would like to discuss or elaborate on? Any references to research that would be helpful to compare? It would be interesting to see what your ideas are, as it seemed a very good overview in understandable language to me.


#6

Nowhere do they argue that the embryonic development of whales perfectly recapitulates their evolutionary history. However, just because their isn’t a perfect recapitulation of their evolutionary history does not mean that there is an absence of evidence found in their development.

Overall, the embryonic atavisms we do see fit the predictions made by the theory of evolution. We don’t see bird embryos with mammalian atavisms such as three middle ear bones or mammary glands. We don’t see mammalian embryos with atavistic feather production. Instead, the atavisms we do see fit into the predicted nested hierarchy. This is why it is evidence for evolution.


(Branko Miletich) #7

True - however as this postulation is invalid/defunct, it should never be used. Using it to support an argument can be deliberately misleading if the author knows it has been debunked. Recapitulation proves nothing nor does it disprove anything.


(Christy Hemphill) #8

It wasn’t used to support his argument. That is your misunderstanding.


(Branko Miletich) #9

then why mention it


(Christy Hemphill) #10

What passage in the article do you think is saying “ontogeny recapitulates phylogeny” or “X because… recapitulation theory”?


(Dennis Venema) #11

Cetacean embryos have forelimbs and hindlimbs at the usual time in development that mammals have both - but the hindlimbs are lost later in development. Forelimb buds and hindlimb buds develop in cetaceans using the same developmental programming found in all mammals. A second developmental program that stops only hindlimb development runs later and disrupts the function of the earlier program.

Cetaceans also have two nostrils (nares) on the front of their faces early in embryogenesis. Later these nares migrate to the top of the head.

These are the facts. How one explains these facts is where theories come in. It just so happens that the theory of evolution nicely explains these facts, as well as all the other ones (genetics, fossils). Of course, I’m using “theory” in the scientific sense.


(George Brooks) #12

@Branko_Miletich,

You seem unable to interpret scientific findings if you find anything in it that reminds you of invalid research. The ability to process scientific findings requires you to be able to distinguish between invalid claims and claims that are limited by the evidence.

The point of the embryonic discussion is to ask why would God have a legless creature like a whale use an embryo that for a short period of time has leg buds identical to mammals that do have legs? That’s all that discussion seeks to
encounter. And instead of providing an intelligent response, you act like someone who doesn’t comprehend scientific distinctions.

Pity.


(George Brooks) #13

@Branko_Miletich,

I suspect English is not your primary language.


#14

What is invalid or defunct as it pertains to developmental atavisms?[quote=“Branko_Miletich, post:7, topic:37519”]
Recapitulation proves nothing nor does it disprove anything.
[/quote]

Pointing to developmental atavisms is not Recapitulation theory.


(Ashwin S) #15

The picture showing the evolution of whales is very pretty. However, it seems, that the oldest whale fossil discovered till date is 49mya.

So, it seems that the form was developed well in advance of the proposed intermediate species!


(George Brooks) #16

@Ashwin_s

Again, you seem to think “God-Guided-Evolution” must be the same as Godless Evolution.

How is it that you keep arriving at this conclusion?


(Ashwin S) #17

Hi Brooks,

If evolution is guided by God all along… How is it different from creationism or Intelligent design?

After all many ID guys believe precisely that God guided evolution. There is only a difference in terminology in that they call this guidance design.


(Phil) #18

My impression is that the main difference is that the ID folks or YEC folks think that God’s involvement is a suitable subject for scientific inquiry, and essentially that proof of God can be found in science, where the ET position is that it is not appropriate to expect proof of God in scientific research. I am sure there is a lot more to it than that, but that is the condensed version as I myself see it.


(A.M. Wolfe) #19

Critically, ID guys believe design is detectable or at least deducible through scientific means. EC folks may either be agnostic on this point, or may believe that design is unlikely to be scientifically detectable, or may believe that such deductions are not part of scientific enquiry by virtue of the type of argument they make and the generally agreed-upon limits of the modern scientific enterprise.

I am not a biologist, but from my limited understanding, this is not necessarily a problem for evolutionary theory, assuming the data actually say what this journalist’s presentation says they do (and I haven’t read the article to know for sure). For one, the earliest intermediate species still fit into the proposed timeline. For two, intermediate forms may outlast more evolved species for many millions of years, which is why we still today have coelacanths, lemurs, platypus and marsupials, among others. For three, earlier specimens of these intermediate species may yet be found (or may have been found already, for all I know as a nonspecialist). For four, this is precisely how science progresses… while the BioLogos article may need updating, this sort of update is a feature of scientific enquiry and not a bug.

All this being said, I haven’t been following your contributions here and don’t know what your particular “angle” here is, so I may be missing the mark in my response to you. At any rate, thanks for the interaction, and all the best to you.

— AMW


(Ashwin S) #20

So basically Science will never find out the Truth… Quite a pessimistic view.

Besides the ID guys are not looking for proof of God. But rather proof of “design”. They are different things.