Only logged in members can reply and interact with the post.
Join SimilarWorlds for FREE »

I Accept the Theory of Evolution

Embryology can be very helpful in showing how our evolutionary history appears during foetal development. There are a few quick and easy examples that spring to mind from all those available: gills, blood vessels, and kidneys.

In the early stages of development, fish embryos have a series of pouches (separated by grooves) near where the head will later develop. These are called the brachial arches - they develop into gills, and the grooves between them develop into the gill slits. It‘s very straightforward.

Other vertebrates have the same structures... including humans. In fact, I once had the opportunity to see these brachial arches for myself on a foetus, and it was fascinating. They‘re not ‘sort of like’ a fish‘s brachial arches... they [i]are[/i] a fish‘s brachial arches. They‘re morphologically completely identical.

Tiktaalik roseae, on the cusp between ocean and land, used gills and lungs, but after the move onto land, gills were superfluous (although Olympic swimming competitions would be very different had we retained them). Sometimes (it‘s very rare) the gill slits fail to close, but it‘s easily corrected via minor surgery once the infant is born.

Blood vessel development in fish is, once again, basic and straightforward, producing six major blood vessels. In mammals (including humans, of course), the same six major blood vessels appear in early foetal development, but then three of them disappear at the same time that our circulatory system stops resembling that of fish and instead becomes identical to the circulatory system of embryonic amphibians. Not similar... [i]identical[/i].
In amphibians, this system simply grows into an adult amphibian circulatory system, but in mammals (including humans, of course) it changes into the circulatory system of embryonic reptiles. Not similar to the circulatory system of embryonic reptiles... [i]identical[/i].
In reptiles, this system simply grows into an adult reptilian circulatory system, but in mammals (including humans, of course), it undergoes further changes (the development of carotid, pulmonary, and dorsal arteries) to become the mammalian circulatory system.

During development, human embryos form three distinctly different types kidneys... the pronephros, the mesonephros, and the metanephros. The first two systems are discarded. The pronephros is the kidney system found in fish and amphibians, the mesonephros is the kidney system found in reptiles, and the metanephros is the kidney system that we eventually use.

From fish to amphibian to reptile to mammal.
No matter how many comforting myths we mutter to ourselves, every foetus carries the truth.
JakeShade · 61-69, M
Janine!
I see we have a biologist in our midst! My daughter is a PhD Molecular Biologist which means I have to study up from time to time to be able to even *talk* to her. I am amazed at the amount of new knowledge that has emerged since my college days. I'm a physicist by training and there is plenty going on there too but Biology is where the explosions are happening!

As a scientist I am often frustrated by popular culture views of science (pro or con) and even worse "Pseudoscience". Too often the pseudoscience "woo" actually has an interesting premise (like a lot of holistic health) but then bozos insist on claiming "scientific evidence" or "proof" when all they have is some anecdotal evidence propped up by the ever-popular confirmation bias!

I am a very spiritual person and don't like interfering with others' "belief systems" on principle. Sadly scientists can treat *their* belief system (entirely mechanistic, logical positivism) as a religion as well.

The "Phylogeny recapitulates Ontogeny" awareness is pretty powerful and the most amazing "new biology" to me is the new awareness of real mechanisms for Lamarckian as well as Darwinian evolution.

As one of your commenters puts a fine point, evolution is highly inefficient by engineering standards but also incredibly robust. Most "junk" DNA turns out to be valuable, even if only holding the "old programming" that allows a more advanced organism to quickly fall back on morphological characteristics that were deprecated (imagine a scenario where said 'tail' is a highly adaptive thing to have again! Why have to go through the *very* inefficient process of "rediscovering" tailness when you have a few thousand base pairs laying around that laready know how to make a pretty good tail on a human!

Good to read you here Janine!
zork0000 · 56-60, M
@JakeShade We could use that tail to control the mouse and keep both hands on the keyboard.
newjaninev2 · 56-60, F
@zork0000 lol! Yes indeed... I want my prehensile tail back!
newjaninev2 · 56-60, F
pone22, you're quite right, and thank you for the illustration!
Yes, I considered mentioning tails (up to 20cm, apparently). Quite understandably, the parents are quite freaked out when such things happen, but the tails are easily removed right after birth... it's a quick and simple procedure.

The important point you make... and it's one that I should have made, but neglected to... is that evolution adds new layers on top of existing ones. That's what we'd expect to see, of course, and that's what we do see.

As an addendum:
[image]
[image]
Some humans have a rudimentary tail muscle (the “extensor coccygis”), [i]identical[/i] to the one that moves the tails of monkeys and other mammals. It still attaches to the coccyx, but since the bones can’t move, the muscle is useless. You may have one and not even know it.
This message was deleted by the author of the main post.
Alabamiangoddess · 51-55, F
@newjaninev2 Tennessean apes
Chattanooga · 56-60, F
@newjaninev2 why are Tennesseans born with tails but Alabamians do not have tails or born with them?
newjaninev2 · 56-60, F
Yes, the common view is that we're running Mac OS X, whereas, in reality, we're running DOS underneath Windows 🙂
We're running bloatware!

I guess that it's the assumption that the programme is completely rewritten that leads to the (rather amusing) belief that each species is part of a chain of directly-linked species, each previous species producing a new species... the image one still sees bandied about of a lemur-like creature directly behind a chimp-like creature directly behind a hominid-like creature directly behind a human, etc.

it always startles me to realise that many people actually think that to be a representation of evolution. Sadly, it seems to be what causes people to think in terms of 'missing links', etc.
This message was deleted by the author of the main post.
This message was deleted by the author of the main post.
It appears you are correct, madame. I think your story needs a lead photo, and I would like to submit the following to you:
[image deleted]
What's interesting about this is that it suggests that embryonic evolution is not about replacement of the old programs, but rather about adding layers on top of historical ones. It looks like genes are just adding information to the end of the program, developing additional steps along the way.
This message was deleted by the author of the main post.
This message was deleted by the author of the main post.
@newjaninev2 I think the layman's view of evolution is that the entire program gets slowly rewritten as it gets more complex. That is NOT what the evidence you are presenting suggests at all. The evidence you are presenting is that the sloppy, old, and incorrect old programs remain. Evolution is adding all the complexity as new programs that only run at the end, after the old ones have finished their unnecessary work.

That's a horribly inefficient system, from the standpoint of system optimization. But it is - however - a very fortunate fingerprint of evolution that presents undeniable evidence in the embryo, as long as you have two eyes that your belief system doesn't require you to keep shut.
zork0000 · 56-60, M
I should have read this before making my clumsy reply on that other post of yours. I bow to your exceptional knowledge.

I love smart women, especially ones in STEM fields.
newjaninev2 · 56-60, F
@zork0000 Yes, he seems to have no stomach for reality intruding into whatever fantasy he'd hoped to spin.
I posted a comment showing him that DNA isn't actually a code, and wham... the thread vanished.
zork0000 · 56-60, M
I was saying that's not how evolution works. You don't set something out ands expect a specific outcome.

Many mutations happen across a broad number of individuals and the ones that end up being most advantageous survive and get passed on.

In the case of his typewriter, you don't expect a book. After waiting for a "God only knows" amount of time, you look in to find possibly a book but you could end up with a DVD, a printing press, a computer, or maybe an extinct species.
newjaninev2 · 56-60, F
@zork0000 Yup, it reflects the underlying anthropocentric hubris of religion that they seem to automatically assume that humanity is somehow some sort of 'goal' of evolution.
This comment is hidden. Show Comment
newjaninev2 · 56-60, F
@TrumanTheTrueman Yes, an interesting case (albeit from the century before last century). While it has been widely claimed that Haeckel was charged with fraud by five professors and convicted by a university court at Jena, there does not appear to be an independently verifiable source for this claim. Still, it's an amusing example of academic in-fighting.
Chattanooga · 56-60, F
People from Louisiana lack animal DNA too they derived and cloned from the Alabamians.
Wraithorn · 51-55, M
Your posts contain a lot of food for thought. I like them.
There isn't any place safe to retire to. :)
I think between technology outpacing our small chimp brains, and the coming evolution of robotic life, it will all be mute soon enough.
This message was deleted by the author of the main post.
Chattanooga · 56-60, F
[youtube=https://m.youtube.com/watch?v=RPh3SFI0e9M]
SW-User
Ontogeny recapitulates phylogeny was a favourite quote of my genetics prof.
newjaninev2 · 56-60, F
@Onecharmingman: Precisely
This message was deleted by the author of the main post.
icyreb · M
and yet evolution isn't putting forth that fish to mammal anymore.. go figure..
Furiousfrog · 31-35, M
Do humans always have to rub their superior kidneys in our face?
This message was deleted by the author of the main post.
This message was deleted by the author of the main post.
This message was deleted by the author of the main post.
newjaninev2 · 56-60, F
(pone22 lights the blue touchpaper and retires to a safe distance...)
newjaninev2 · 56-60, F
skymike, sorry, I'm not sure what you mean. Could you clarify for me?
CookieLuvsBunny · 31-35, F
Ontology recapitulates phylogeny

 
Post Comment