How ancient whales lost their legs, got sleek and conquered the oceans

EurekAlert (AAAS) ^ | 22 May 2006 | Staff

[PatrickHenry]

When ancient whales finally parted company with the last remnants of their legs about 35 million years ago, a relatively sudden genetic event may have crowned an eons-long shrinking process.

An international group of scientists led by Hans Thewissen, Ph.D., a professor of anatomy at Northeastern Ohio Universities College of Medicine, has used developmental data from contemporary spotted dolphins and fossils of ancient whales to try to pinpoint the genetic changes that could have caused whales, dolphins and porpoises to lose their hind limbs.

More than 50 million years ago the ancestors of whales and dolphins were four-footed land animals, not unlike large dogs. They became the sleek swimmers we recognize today during the next 15 million years, losing their hind limbs in a dramatic example of evolutionary change.

"We can see from fossils that whales clearly lived on land - they actually share a common ancestor with hippos, camels and deer," said team member Martin Cohn, Ph.D., a developmental biologist and associate professor with the UF departments of zoology and anatomy and cell biology and a member of the UF Genetics Institute. "Their transition to an aquatic lifestyle occurred long before they eliminated their hind limbs. During the transition, their limbs became smaller, but they kept the same number and arrangement of hind limb bones as their terrestrial ancestors."

In findings to be published this week in the Proceedings of the National Academy of Sciences, scientists say the gradual shrinkage of the whales' hind limbs over 15 million years was the result of slowly accumulated genetic changes that influenced the size of the limbs and that these changes happened sometime late in development, during the fetal period.

However, the actual loss of the hind limb occurred much further along in the evolutionary process, when a drastic change occurred to inactivate a gene essential for limb development. This gene - called Sonic hedgehog - functions during the first quarter of gestation in the embryonic period of the animals' development, before the fetal period.

In all limbed vertebrates, Sonic hedgehog is required for normal limbs to develop beyond the knee and elbow joints. Because ancient whales' hind limbs remained perfectly formed all the way to the toes even as they became smaller suggests that Sonic hedgehog was still functioning to pattern the limb skeleton.

The new research shows that, near the end of 15 million years, with the hind limbs of ancient whales nonfunctional and all but gone, lack of Sonic hedgehog clearly comes into play. While the animals still may have developed embryonic hind limb buds, as happens in today's spotted dolphins, they didn't have the Sonic hedgehog required to grow a complete or even partial limb, although it is active elsewhere in the embryo.

The team also showed why Sonic hedgehog became inactive and all traces of hind limbs vanished at the end of this stage of whale evolution, said Cohn. A gene called Hand2, which normally functions as a switch to turn on Sonic hedgehog, was shown to be inactive in the hind limb buds of dolphins. Without it, limb development grinds to a halt.

"By integrating data from fossils with developmental data from embryonic dolphins, we were able to trace these genetic changes to the point in time when they happened," Thewissen said.

"Studies on swimming in mammals show that a sleek body is necessary for efficient swimming, because projecting organs such as rudimentary hind limbs cause a lot of drag, and slow a swimmer down," said Thewissen, who spends about a month every year in Pakistan and India collecting fossils that document the land-to-water transition of whales.

Researchers say the findings tend to support traditional evolutionary theory, a la Charles Darwin, that says minor changes over vast expanses of time add up to big changes. And while Sonic hedgehog's role in the evolution of hind limbs in ancient whales is becoming apparent, it is still not fully defined.

"It's clear when ancient whales lost all vestiges of the limb it was probably triggered by loss of Sonic hedgehog," said Clifford Tabin, Ph.D., a professor of genetics at Harvard Medical School who was not involved in the research. "But it's hard to say for certain because you're looking at events long after they occurred. As they suggest, there could have been a continual decrease in Sonic as the limbs reduced until the modern version of the animal arrived."

The study itself, combining fossil and developmental data, is notable, Tabin said.

"Whales went through this remarkable transformation to become more like the ancestral fish," Tabin said. "Convergence of evolutionary studies and developmental genetics give us another piece in this growing tapestry of how genetic changes lead to morphological change. It is a remarkable process that was achieved simply and led to profound consequences in how whales were able to survive. Only now in the last five years are we developing this understanding of how the world of evolution is controlled genetically."

###

In addition to UF and Northeastern Ohio Universities College of Medicine, scientists from the Natural History Museum of Los Angeles County and the Indian Institute of Technology were involved in the research. Financial support was provided by the National Science Foundation, the National Institutes of Health and the Indian Department of Science and Technology, New Delhi.

[jerryem]

And God made man in his image, now which God and which image, the Southern Baptist does not think of a desert nomad from Chad, or a native of New Guinea as his blood brothers, (they look real different) so please explain what color was Adam and what color was Eve, so either the Bible is wrong, or Chinese dont exist, (but they tell me that one in three people is a Chinese)

[ScubieNuc]

I've reread your rant and here's what I see...

"I wonder if you could enlighten me as to where Genesis fits into the hundreds of millions of years of evolution,"

Obviously, because I am a Creationist, there is no "hundreds of millions of years of evolution" in Genesis, therefore there is no "fitting into."

"facts ( or fiction?)
32% of the worlds population is Christian.
66% is not
there is 34,000 separate Christian groups, because, they all interpret the scriptures differently. when following your arguments it would mean that32% believe that the world is flat and 66% believe the world is round"

The short story is...you make lousy comparisons. If it soothes your mind to think that Christians reject proven facts (round earth), then nothing I post can convince you otherwise.

My question to you is this...If you truely believe what you posted, why does that bother you? If you told me that the earth was actually a giant meatball and if I didn't worship the invisible spagetti strand,then I would burn in the fires of Rague...I would roll my eyes, shrug my shoulders, and say, "Oooh Kayyyy, Dude." and walk away.

You on the other hand seek to "enlighten" me through superior sarcasm. Which is crazier? The insane person, or the person trying to enlighten the insane person?

Sincerely

[ScubieNuc]

"4.5 billion years; the universe is about 15 billion years old though. The Earth was not made in a *cosmic boom* 4.5 billion years ago. That's a basic error that shows you know next to nothing about something you are attacking."

Well thanks for the update. I find it interesting that about 10 years ago the number was about 4.5 billion. Another nice example of how precise evolutionary dating is.

Either way, it doesn't change my question to the person I was writting to. 4 billion or 15 billion years of mutating and death isn't consistant with the overall theme of the Bible.

As far as your comment about "attacking", that's backward. If you took the time to actually read the correspondence, I was defending the Bible.

The person I was writting to believes that the Bible and evolution are compatable, I do not. You are correct that I am not learned in the Great and Mighty Works of your god Evolution, but I do know a thing or two about the Bible. As a Christian, it is my duty to do my best to spread the news of the Bible, so that is what I was doing.

Sincerely

[CarolinaGuitarman]

"I find it interesting that about 10 years ago the number was about 4.5 billion. Another nice example of how precise evolutionary dating is."

a) The age of the universe was not said to be 4.5 billion years 10 years ago, or 20. Or 30. It has been calculated to be between 10-20 billion years for a long time; it has in the last 10 years been put at the 15 billion year mark. The Earth has been known to be 4.5 billion years old for a while now too, and was known to be quite a bit younger than the universe as a whole. Your wrong.

b) The age of the universe has absolutely nothing to do with evolutionary theory. Nothing.

"As far as your comment about "attacking", that's backward. If you took the time to actually read the correspondence, I was defending the Bible. "

I didn't say you were attacking the Bible. You were attacking science without having the knowledge to do so.

"You are correct that I am not learned in the Great and Mighty Works of your god Evolution, but I do know a thing or two about the Bible."

Again, what you attacked (the age of the universe) has nothing to do with evolution. What yo are attacking is cosmology and the physics that goes with it.

[CarolinaGuitarman]

That should be *you're*, not *your*.

[ScubieNuc]

"Rom 1:22 Professing themselves to be wise, they became fools,

These quotes from Romans are great. How do you know that Paul's not talking about creationists, here? One doesn't become wise by professing themselves wise, one becomes wise through hard work and study of the world around him."

Actually the Bible says that real wisdom comes from God, not study of the world. By studying you gain knowledge, wisdom is correct application of knowledge. Only God knows what is the correct application, sometimes we guess right, but then that's luck.

Jam 1:5 If any of you lack wisdom, let him ask of God, that giveth to all [men] liberally, and upbraideth not; and it shall be given him.

1Cr 3:18 Let no man deceive himself. If any man among you seemeth to be wise in this world, let him become a fool, that he may be wise.

1Cr 3:19 For the wisdom of this world is foolishness with God. For it is written, He taketh the wise in their own craftiness.

1Cr 3:20 And again, The Lord knoweth the thoughts of the wise, that they are vain.

" Of course, taking the creationist route is easier - you can learn everything you need to know about science in about five minutes! I don't think God put us here to turn a blind eye to the clues he laid out for us to investigate His creation. "

Prior to that statement, you posted a whole host of "Show me how God did this" type questions. The short answer is "I don't know." But then again, he made Adam and Eve as adults not babies, so he could make things in an older state. Alot of your questions come from our human view point that everything must start small and grow big and old. God doesn't have to work in our limited parameters.

Now before I get a TON of posts saying that doesn't prove anything...I will agree, it doesn't. I accept that God did it on faith. The "how" he did it, I don't have the answer for.

Your other statement is too broad..."everything you can learn about science in five minutes." I'm talking Origins ideas, not ALL of science,and I never said or heard anyone say that all you need to learn about science you can learn in the Bible or in 5 minutes.

As far as studying his creation...ABSOLUTELY, go do it. Just differenciate between what you can observe through consistant testing, and what you can dublicate, with what is thought to have happened. That's where I and most Christians I know draw the line.

"If you actually investigate the science and look at these Biblical passages from a standpoint of informed reason"

Now, I'm going to assume that you are a Christian...if you are then that statement is wrong. Your saying that worldly knowledge will guide you in understanding God's word. Reread the above scriptures plus this one....

Jhn 14:26 But the Comforter, [which is] the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you

You need the Holy Spirit to teach you what is in the Bible, because it is spiritual.

1Cr 2:13 Which things also we speak, not in the words which man's wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.

1Cr 2:14 But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know [them], because they are spiritually discerned.

"I don't honestly know myself. All I know is that if one promulgates the notion that a religion requires belief in a 6000 year-old-earth where creatures appeared out of thin air and all gathered together in pairs to ride on a barge to escape a worldwide flood that left no evidence of its existence, one only succeeds in making that religion look utterly ridiculous.

This is what Jesus requires...

Rom 10:9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.

Rom 10:10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.

I sincerely pray that you read the scriptures with a God seeking heart. My primary desire is to show the truth (Jesus), not convert people to a religion.

Sincerely

[Almagest]

The person I was writting to believes that the Bible and evolution are compatable, I do not.

How does that person's belief constitute an "attack on the Bible"? It seems to be nothing more than a disagreement with you over the interpretation of some passages.

You are correct that I am not learned in the Great and Mighty Works of your god Evolution, but I do know a thing or two about the Bible.

Do you know the parts about being charitable, even to your "enemies"? Do you know the parts about being patient and kind to everyone? Do you really, in your deepest heart, believe that your characterization above was what the Bible teaches you to do? To castigate someone with such an obviously false, and outrageous accusation?

There are quite a few passages in the Bible -- passages that I believe you and I would agree on concerning their meaning -- that speak to this approach you have chosen to take. But -- I have had to become enured to the fact that so many self-professed Christians out to "defend the Bible" really don't care much at all about what it says concerning their attitudes and behavior.

It's sad -- but so many of them give evidence of having no conscience at all. I have to confess -- I don't understand it. This is not the Christianity I knew. Frankly -- I continue to be shocked at the incredible hatefulness and cruelty I see in here.

[ScubieNuc]

Relax mr. Science-guy.

You've missed the point again. Part of it is my fault. I see my error...The Universe is believed to be 15 billion and the Earth is believed to be 4.5 billion. Correction noted.

You are assuming that I am attacking Evolution. Wrong. My point to the person I was corresponding with was in defense of the Bible. Therefore your correction of my bad summation of what evolution says doesn't matter. Either way it doesn't fit with the Bible.

Your desire to split hairs may serve some purpose of yours, but frankly I don't see it. First, I wasn't directly talking to you. Second, I have tried to be consistent with defining (with those I am corresponding to) that I am talking about ORIGINS ideas.

I understand that the text book meaning of Evolution doesn't deal with origins, however, you are being naive to think that most people are talking about origins when they say evolution, and I'm not just talking about Creationists here.

I can see you want to get into a deep scientific throw-down with me, but frankly I'm not interested, nor do I have the time right now.

Have a good night.

Sincerely

[ScubieNuc]

"How does that person's belief constitute an "attack on the Bible"? It seems to be nothing more than a disagreement with you over the interpretation of some passages."

Whoa! Maybe I typed something without doing a thorough enough proof read, but that is not what I was trying to say. Guitarman said I was attacking Evolution. I said I wasn't attacking evolution, I was defending the Bible. Maybe I should have said that I was defending my belief in how evolution isn't compatable with the Bible.

"Do you know the parts about being charitable, even to your "enemies"? Do you know the parts about being patient and kind to everyone? Do you really, in your deepest heart, believe that your characterization above was what the Bible teaches you to do? To castigate someone with such an obviously false, and outrageous accusation?"

You are correct. Guilty as charged. I have a sarcastic approach that definately comes out real bad sometimes on line. I sincerely apologize for being un-Christ like.

"I continue to be shocked at the incredible hatefulness and cruelty I see in here."

I must ask this in complete seriousness...Do you really read my posts as hatefull and cruel? Do you read any hate and cruelty in the Evos posts?

Sincerely

[ScubieNuc]

"... you are being naive to think that most people are talking about origins when they say evolution,"

AREN'T is what I meant. Ooops

[CarolinaGuitarman]

"You are assuming that I am attacking Evolution."

I said no such thing. I said you were attacking cosmology.

"Therefore your correction of my bad summation of what evolution says doesn't matter."

Nothing you said had anything to do with evolution; I corrected your mistakes about cosmology.

"First, I wasn't directly talking to you."

Too bad.

"I understand that the text book meaning of Evolution doesn't deal with origins, however, you are being naive to think that most people are talking about origins when they say evolution, and I'm not just talking about Creationists here."

Evolution deals with the origins of species from already existing species. That some ignorant people think it has something to do with the origins of the universe is something that needs to be corrected.

"I can see you want to get into a deep scientific throw-down with me..."

I don't think I have to worry about that.

[CarolinaGuitarman]

"Guitarman said I was attacking Evolution."

I said no such thing. Stop inventing things. I clearly said that you were attacking cosmology, which I clearly said has nothing to do with evolutionary theory.

[Fledermaus]

Boy, the stuff they'll make up to "prove" Darwin.

[Almagest]

"I must ask this in complete seriousness...Do you really read my posts as hatefull and cruel?"


In all seriousness -- most of them, yes. Incredibly so. Along with most of the posts from other YECers.


"Do you read any hate and cruelty in the Evos posts?"


In all seriousness, here is what I see. I see enormous patience from many of them -- patience with the incredibly foolish statements and outrageous lies that are trotted out again and again and again, even after having been corrected dozens of times.

I see attempts to explain, to teach, to point the way. I see frustration creeping in after a while, and that tends to cause some people to snarl. Also -- we often use humor just to break the tension.

I also see a few who say some cruel things to/about YECers and Christians -- occasionally. I also see some of them make poor arguments, especially concerning religious matters.

But the balance is extremely weighted the other way. I can't help but see that. And I am speaking as someone who was a YEC for a long time. I don't remember the viciousness, the slander, the hatefulness from that time. I do remember the self-righteousness and the false accusations against people's motives and character -- but not the viciousness I see now.

I'm sorry -- but that's what I see. Most of the YEC's have been incredibly hateful and dishonest -- in most of their posts. There are almost no real discussions of the science involved, because they are all taken up with the bickering that is being deliberately stirred up. On most other threads, those kinds of posts are called "trolling."

Do the religion threads get a lot of anti-religion people constantly jumping in and carping at them like this? Not that I have noticed -- at least not as a regular thing, like we get on the crevo threads.

YMMV.

[ScubieNuc]

"I said no such thing. Stop inventing things. I clearly said that you were attacking cosmology, which I clearly said has nothing to do with evolutionary theory."

Why you are so aggitated, I'll never know. If anyone really cares they can check post #304. In it you actually say that I was attacking science, not cosmology. That term shows up in some later post. So we're both technically wrong.

Sincerely

[ScubieNuc]

Oops I did it again. You did stay cosmology in that post as well. I still don't see what the big deal is. What ever!

[CarolinaGuitarman]

"Why you are so aggitated, I'll never know."

Because you are saying I said things I didn't. I said the opposite.

"If anyone really cares they can check post #304. In it you actually say that I was attacking science, not cosmology. That term shows up in some later post. So we're both technically wrong."

No, I was 100% correct, you were wrong. I said in #304 that what you were talking about is cosmology. I ended the post with this:

*Again, what you attacked (the age of the universe) has nothing to do with evolution. What you are attacking is cosmology and the physics that goes with it.*

[CarolinaGuitarman]

"You did stay cosmology in that post as well. I still don't see what the big deal is. What ever!"

Correction noted.

[Almagest]

"Oops I did it again. You did stay cosmology in that post as well. I still don't see what the big deal is. What ever!"


I give up! First you apologize, and then you go right back to it! Didn't YOU defend yourself to ME when you thought you were quoted out of context? Didn't you just defend yourself against this other poster for the same reason?

Seemed to be a big deal when you thought it was YOU being mischaracterized. Ever heard of "do unto others"?????

I give up.

[gedeon3]

This is total b.s.; Whales never had legs. This is one of the big lies of science.