Simple to Complex - Reproduction

Hello,Just a few points: Fair enough, embryogenesis does not include the processes of random mutation and selection and should not be used as a direct analogy to evolution (eg look embryos are evolving all the time!!). I don’t think that’s what Dan meant though. What can be said in reply to the tired creationist bacteria-to-man dogma is that evolution took it a bit at a time, and this can be demonstrated by looking at events in development. From single cell zygote to a multi-cellular ball, to having two germ layers and then developing three, it’s all about small steps. The steps involved in embryogenesis are echoed, not only by current organisms but also by the fossil record. The ‘significant changes’ to the genome you state are just not possible start to become less substantial if you look at it like this. How much of a change would you think is required for going from single to multi-celled for example?Which leads me to I’m pretty sure this is not true. Crashfrog has frequently put up a link to a paper that reported just that — a single celled organism evolving into a multi-cellular, and stable colony, I’ll try and dig it up for you. On top of this, organisms like slime moulds are well known for forming multi-cellular aggregates in response to environmental conditions, is it really hard to accept this becoming a permanent arrangement?And I know this is a fair bit off-topic, but it’s one of my personal bug-bears: from the same paragraph (my emphasis) This is not true. There is a cartload of molecular evidence pointing to common ancestry. So it's not an act of faith it's a position based on evidence. If you don’t accept this then maybe we could take it to another topic

Hello again, I think you misunderstood what I was trying to get across here. I wasn’t commenting on the freak luck of finding an embryonic dinosaur or a pre-natal mammoth, I was saying that the order we see things appear in the fossil record apes that seen during development.When we look at the fossil record what is the order we find things cropping up? Single cellssimple multi-cellularorganisms with two germ layers (like jelly fish)organisms with three germ layersWhen we look at embryogenesis what do we see? A single cella ball of cellstwo cell layersthree cell layers. It echoes the pattern suggested by the fossil record, and emphasises the step by step nature of evolution.It’s no longer a matter of single cell to human and a big hand-wavey statement about numerous and significant changes, it’s all about taking it a step at a time: as already pointed out single- to multi- celled is not such a big step (and experimentally observed), the process of developing two germ layers (gastrulation) is also being investigated. Dismissing it all as ‘hypothetical’ does great disservice to the amount of evidence out there. Unfortunately, it never seems to be just that (a little dig). It’s something that creationists throw into the argument willy-nilly, without expecting to be challenged on it (which is why I always bite ).For example, you threw this into the last post: It’s not purely hypothetical, there is a great deal of evidence for common ancestry!

Hello again, Nice try, but no I wasn’t referring to Haekal’s biogenetic law. As you rightly point out, the idea that an embryo passes through all of the adult stages of it’s descendents as it develops was thrown out quite sometime ago as a bucket-load of fraudulent codswallop. I was talking about the relatively new (and very much alive) concept of evolutionary developmental biology (understandably known as Evo-Devo).Here’s another link to Talkorigins talking about Haeckel and misrepresentation of Evo-Devo by a particular creationist. These sections are particulary pertinent:

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What modern developmental biology has been discovering is that these earliest stages in different vertebrate embryos are substantially similar. The differences are superficial, and in many cases a consequence of different amounts of maternal investment

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The processes of cell signaling important in inducing new tissues during gastrulation are similar in all vertebrates, and the same answers are turning up in fish and mice, despite the morphological differences in their layouts.

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So when you say: It’s all about looking at the type of animals that appear in the fossil record and looking at embryogenesis of modern equivalents. Evo-Devo uses the techniques and knowledge from the field of developmental biology and then applies them to evolution. If we share common ancestry with something, then it stands to reason that we share developmental processes. That’s what we see: common genes controlling common processes, and a step-by-step introduction of these processes through time in the fossil record.