0

The theory of evolution claims that birds evolved from dinosaurs only by mutation, genetic drift, migration and natural selection.

However, it seems to me that wings were not selectively advantageous for dinosaurs.

Would you show me a book or a paper which explains this point in detail with academic accuracy? Level of the book or the paper should have detailed information for an advanced reader.

Makoto Kato
  • 163
  • 1
  • 7
  • 2
    An introductory course to evolutionary biology such as Understanding Evolution for example might help you. – Remi.b Nov 07 '15 at 18:50
  • @Remi.b I'm looking for a book or a paper (or an internet site) that explains the evolution of dinosaurs to birds in detail with accademic accuracy. Does that site you mentioned have such an account? If yes, would you please show us a link to it? I checked the site, but I was unable to find the one. – Makoto Kato Nov 07 '15 at 20:53
  • No the site I linked is not specific to your question. But having a better understanding of evolutionary processes in general will help you to answer the specific questions you may have (such as the one you are asking in this post). – Remi.b Nov 07 '15 at 20:56
  • You might want to have a look at this post to avoid potential semantic issues about what a dinosaur is. – Remi.b Nov 07 '15 at 20:58
  • The question is unfortunately too broad. There have been many changes from the ancestors of modern day birds and modern day birds. You should reduce your question to one specific trait and also probably precise whether you are interested in knowing the phenotypic intermediate stages or the specific genes involved in the evolution of this specific trait. – Remi.b Nov 07 '15 at 23:36
  • @Remi.b "The question is unfortunately too broad." Why on earth do you think a question is too broad that asks for a book or a paper on a specific subject? – Makoto Kato Nov 12 '15 at 18:21
  • @MakotoKato this is broad because one would have to explain you about phylogenetic and palaeontological methods. These are not really laboratory simulations of macroevolution but inferences drawn from what is observed from the remains of these organisms. – WYSIWYG Nov 25 '15 at 05:30
  • @MakotoKato You will hopefully find this popular article interesting and useful: How Dinosaurs Shrank and Became Birds (it has also been reprinted in Scientific American) – fileunderwater Nov 25 '15 at 09:49
  • @WYSIWYG You talk as if you know the answer. In any case, I'm asking for a book or paper that answers my question. What's wrong with it? – Makoto Kato Nov 25 '15 at 13:29
  • Try asking about a particular aspect such what you seem to be interested in, the early evolution of wings and flight in maniraptorans. the entire process of birds evolving from dinosaurs would fill several large books, hence too broad. – John May 09 '18 at 00:13

1 Answers1

4

First of all, dinosaurs did not evolve to birds. A better way of saying it is that modern birds evolved from a particular type of dinosaur. That, however, is not the same as the blanket statement "dinosaurs evolved to birds". The latter implies that dinosaurs somehow morphed into birds and stopped being dinosaurs. What actually happens is that a species starts changing and, eventually, a sub-population of that species has changed so much that we call it a new species. It is a subtle distinction but important.

As for a specific paper, no we don't have anything like that for any specific examples. What we have is a huge collection of observations all of which point to the process of speciation occurring via the processes of mutation and natural selection. It's impossible to know the precise series of mutations that led to the creation of a new species for a variety of reasons.

All we have is the current species. If we know an ancestor, we can deduce a possible path that leads from the genome of the ancestor to the genome of the target species but we have no way of knowing whether that specific path was followed. For an analogy, consider computers. If I were to give you a modern desktop PC and one of the first computers:

old and new computers

You might be able to guess certain changes that were made to the old ones in order to build something like the new ones but would you be able to figure out every single step along the way? How would you detect all the attempts that failed? The ideas that didn't pan out? Would you be able to infer the existence of floppy disks, for example?

The same problem applies to species. It is essentially impossible to infer the precise series of mutations that led species B to split from species A. Especially since, usually, this happens through species A.1, A.2, A.2.1, A.3 etc, and all we have is species B.

Add to that the fact that evolution is not a linear process, there are many dead ends (way more than in computers), and the story gets even harder to understand. This graphic illustrates it quite well:

enter image description here

Obviously, if you have the first red dot on the far left and the last blue on on the far right, it will be impossible to infer the entire evolutionary history linking these species.

So, with this in mind, given that dinosaurs and birds share a common ancestor, it is essentially impossible to get the full, true, path that led from that ancestor to either dinosaurs or birds. More importantly, as shown in the image above, dinosaurs did not evolve into birds in the first place so the question is moot.

terdon
  • 12,803
  • 5
  • 46
  • 73
  • If the "common ancestor" was a dinosaur, then it would not be incorrect to suggest that birds evolved from dinosaurs. – Harry Vervet Nov 07 '15 at 21:43
  • Could you give me a clue how reptilians(I hope the nomenclature is more accurate than dinosaurs), for example, grew wings and lost most of bone marrows? It seems to me that those features are not advantageous for them to survive unless they were able to fly. – Makoto Kato Nov 07 '15 at 21:45
  • @vervet as far as I know, that's not the case. I may be wrong though. – terdon Nov 07 '15 at 21:55
  • @MakotoKato well, for a clue, have a look at this answer about bats. Look at the gliding mice. You can imagine similar intermediate steps. – terdon Nov 07 '15 at 21:56
  • 1
    @terdon "First of all, dinosaurs did not evolve to birds. That is a common misconception. You might want to have a look at the answers here. What you're probably thinking of is that modern birds and dinosaurs share a common ancestor." I beg to disagree. http://evolution.berkeley.edu/evolibrary/article/evograms_06 "The discovery that birds evolved from small carnivorous dinosaurs of the Late Jurassic" – Makoto Kato Nov 22 '15 at 20:35
  • @MakotoKato thanks for the link. I hadn't expressed myself clearly. My main point was that while modern birds may well be descendants of certain dinosaurs, you can't say that dinosaurs evolved to birds. Only that birds evolved from dinosaurs. The first statement implies that dinosaurs were replaced by birds rather than simply that they gave rise to them. – terdon Nov 23 '15 at 14:07
  • 1
    @MakotoKato you greatly misunderstand evolution when you presuppose that all the traits that exist have to be selectively beneficial. We know that the vast majority of new mutations are near-neutral and selection can be quite weak. Also, a trait may simply piggyback on other beneficial traits - take a gene for resistance to a pathogen, for instance and a gene for fur colour in a predator free environment where the disease is selective; if the two traits emerge in the same lineage fur colour will be selected for just because disease resistance is selected for. – Ankur Chakravarthy Nov 24 '15 at 15:05
  • @AnkurChakravarthy "We know that the vast majority of new mutations are near-neutral and selection can be quite weak." Suppose wings were selectively neutral for dinosaurs. Then the probability of the evolution of birds from dinosaurs would be very very very small. It would be like a monky typing entire Shakespeare's Hamlet. – Makoto Kato Nov 24 '15 at 17:02
  • @MakotoKato perhaps, but that wouldn't mean it couldn't happen. More importantly, wings would never be selectively neutral. They immediately open up an entire new ecological niche and all sorts of new defensive options. They would most certainly not be neutral. – terdon Nov 24 '15 at 17:14
  • @terdon "but that wouldn't mean it couldn't happen." In realty, no, it could never happen. "wings would never be selectively neutral." If they were selectively negative, birds would not exist. The only option is that they were selectively positive. But this argument is flawed because it assumes that the theory is correct. – Makoto Kato Nov 24 '15 at 20:37
  • Um no, firstly , depending on population size even deleterious alleles can be fixed by drift.

    The other thing is neutral traits can be fixed as if under selection due to chromosomal linkage with another trait that is subject to selection ; this effect is called genetic hitchhiking.

    There is no evidence that wings at all stages had to be of adaptive benefit for the evolution of birds to be possible. The notion that birds couldn't have evolved if wings weren't selected for is wrong.

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1459830/

     – Ankur Chakravarthy Nov 25 '15 at 18:29
  • That wings could be selected for, on the other hand, also enjoys support; one only needs to look at the rapid diversification of Pterosaur lineages for a period of nearly 75 million years, and even after that Pterosaur diversity did not drop off a cliff until near the end of the cretaceous. – Ankur Chakravarthy Nov 25 '15 at 18:32