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    The Amphibious Ancestors Of Whales
    By Michael White | February 4th 2009 09:57 PM | 23 comments | Print | E-mail | Track Comments
    About Michael

    Welcome to Adaptive Complexity, where I write about genomics, systems biology, evolution, and the connection between science and literature,

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    Show Me The Science Month Day 9

    In what is now central Pakistan, an eight-and-a-half foot long, pregnant aquatic mammal went belly-up, and sank to the bottom of the shallow coastal waters. 47 million years later, a huckster by the name of Duane Gish denied that such mammals ever existed:

    There simply are no transitional forms in the fossil record between the marine mammals and their supposed land mammal ancestors . . . It is quite entertaining, starting with cows, pigs, or buffaloes, to attempt to visualize what the intermediates may have looked like. Starting with a cow, one could even imagine one line of descent which prematurely became extinct, due to what might be called an “udder failure” (Gish DT. Evolution: The Challenge of the Fossil Record. El Cajon (CA): Creation-Life Publishers, 1985 p.78-9, quoted at Talk Origins).


    Gish may have found it entertaining to imagine what a half-whale, half-buffalo looked like, but today's scientists don't have to imagine the appearance of land-based ancestors of whales. The fossil series leading up to whales tells a very detailed and remarkable story of how furry, four-legged land mammals eventually gave rise to behemoth marine descendants. A spectacular fossil find, reported yesterday in PLoS One, reveals some amazing details from the evolutionary history of whales.



    Figure 5A from Gingerich, et al.


    Scientists working at the University of Michigan in the US and the University of Bonn in Germany found the fossil skeletons of two adult amphibious mammals, named Maiacetus inuus, that lived 47 million years ago. One was a male, and the other was a near-term pregnant female. This spectacular find has been covered extensively in the news and in the blogosphere. (More here, and a picture of one fossil reconstruction is here.)

    What is impressive about this fossil find is how much scientists can learn about the lifestyle of a creature that lived 47 million years ago. Nobody was around 50 million years ago to observe what was going on, critics like to say, but, as with clues at a crime scene, we can piece together some very big pieces of the puzzle with fossil finds like this.

    Some context: numerous fossil specimens of various proto-whales have turned up. (For an impressive summary with lots of pictures, check this out. More in this PDF document.) Two major classes of so-called transitional species are the basilosaurids, which were fully aquatic whale-like animals with the powerful swimming tails of modern modern whales, but remnants of their ancestral land life as well, such tiny hind legs, skulls, and teeth that more closely resemble those of their land-based ancestors; and the amphibious protocetids, which were leg-powered swimmers. These amphibious mammals, perhaps much like crocodiles, spent the bulk of their time in the water, but came to land to rest and give birth. Their legs, while able to support the animal's weight on dry land, weren't that great for getting around; these legs were adapted for swimming.


    Figure 1 from Gingerich, et al. A completely aquatic basilosaurid shown at the top, and the amphibious Maiacetus at bottom.


    The recently discovered fossil Maiacetus was an amphibious mammal, and the lucky find of a near-term fetus fossil has enabled the scientists to deduce something about the lifestyle of this animal. The researchers write that "specimens this complete are virtual ‘Rosetta stones’ providing insight into functional capabilities and life history of extinct animals that cannot be gained any other way."

    For starters, finding only one fetal skeleton inside of the female Maiacetus sugests that these animals had singlet pregnancies, just like today's present-day amphibious mammals. Because the fetus was positioned to be born head-first, the researchers conclude that Maiacetus gave birth on land. No whales or other completely aquatic mammals give birth head-first (this strategy probably prevents the infants from drowning during the birth process), and this idea that Maiacetus gave birth on land is consistent with the other skeletal features that suggest this was an amphibious animal that spent some time out of the water.

    In fact, the position of the fetus is so telling that the researchers make a prediction of what we expect to find if a fossil fetus of a fully-aquatic basilosaurid is found: that fetus will be positioned with its tail, not its head, towards the birth canal, consistent with the typical lifestyle of a fully aquatic mammal.

    The fetus fossil also provides clues about the feeding habits of a newborn Maiacetus. By examining the developmental state of the fetus' teeth, the scientists can tell that these animals were what are called "precocial mammals" - mammals that hit the ground running (or swimming) from the moment they are born. The fetal Maiacetus has fairly well-developed teeth, comparable to newborns of some deer species. Newborn Maiacetus had to come out ready to swim and eat solid food.

    Near the fossil of the pregnant female, the scientists found a fossil of a male. The male fossil was much larger, about 12% longer which most likely means it was 39% heavier than the female. Such a dramatic difference in size between males and females is called sexual dimorphism, and, in the case of larger males, is the result of the evolutionary pressure of male-male competition. The extent of male-male competition usually reflects the mating habits of the species, and so, based on the sexual dimorphism of Maiacetus, the researchers ventured some guesses about the family life of this animal.

    We can see how sexual dimorphism and mating behavior works in modern mammals today. At one extreme, you can have huge males with large harems that they ferociously defend in titanic battles against competing males (think elephant seals). For this to work, dominant males need to be able to keep their females close together - food and shelter have to be concentrated in a small area. In cases where the environment makes harems like this impractical, you have something called dispersed mating, where the females are spread out over a larger area and harems, if they exist, are much smaller. Competition among males is reduced, and the body-size differences between males and females are less dramatic. The body size difference between sexes in Maiacetus, when compared with modern aquatic and semi-aquatic mammals, falls below the the range usually seen for harem mating, and so the researchers conclude that these animals were more dispersed:


    Figure 15 from Gingerich, et al.


    This means that food and shelter were probably more dispersed in the Maiacetus environment as well, and in fact the researchers note that:

    This is corroborated by the geographically extensive but environmentally uniform shallow marine deposits of the Habib Rahi Formation, which were deposited on a broad, shallow marine shelf that would have provided little spatial aggregation of food or shelter.

    This research shows how powerful fossils can be for reconstructing the history of ancient life. One caveat to keep in mind of course is that these are only single examples of Maiacetus. How do we know that the head-down fetus wasn't an abnormality? How do we know that this particular male wasn't some sort of freak of nature - abnormally large or small? We don't know - the conclusions about birth habits and sexual dimorphism could be wrong, because they are based on these single specimens. But as the paper makes clear, these conclusions are also based on multiple lines of consistent evidence, so the researchers have made very reasonable guesses.

    We're one third of the way through 30 Days of Evolution Blogging, and already we've encountered an amazing find, published just this week. Every month, evolutionary biologists produce exciting new discoveries. Pick a month, any month, then follow the field every day for that month, and you're bound to learn something amazing. Evolutionary biology is one of the most active, fascinating sciences around today. Its success is due to a well-established body of theory, combined with remarkable technology in molecular biology and genetics, and technology for finding, dating, and analyzing fossils.

    This is the kind of stuff that should be taught in schools. This is what will get kids excited about science. Evolutionary biology needs to be a full part of the biology curriculum; it should not be downplayed by teachers out of fear, and it should not be watered down with spurious "evidence against evolution." This is incredible science, not ideology, not a conspiracy to assault anyone's religion.

    Join me tomorrow, here at Adaptive Complexity, for day 10 of Show Me The Science Month. Evolution as a science is alive and well. Each day I will blog about a paper related to evolution published in 2009.

    Comments

    ..reasonable "guessing"?? Beautiful...

    adaptivecomplexity
    And what exactly is that supposed to prove, Perry? So scientists made guesses about the lifestyle of this animal - what's the problem?

    What they did not guess at is the age of this fossil and the clear transitional morphological features - the evidence is clear. If you don't believe in the evolution of whales, let's hear your scientific explanation for the fossil record.
    Mike
    ...you sure are touchy sometimes. I would suggest Michael that the evidence is "not" so clear in any other respect than this is a fossilized example of an existing animal, nothing more. When someone has invested their life in the search of "transitional" links, and has also comitted their core belief system to there being an example out there somewhere then the deck is stacked from the beginning. So much is made of those of us who adhere to ID that we see "what" we want to see" that is it beyond the realm of possiblity that the same kind of observation could happen by one who believes in evolution? You must admit that the search has been long and extensive and yielded very little and nothing concrete. I have zero problem with a Scientist who "guesses about the lifestyle of a lineup of bones on a table pulled from the Earth...have fun, speculation is fun, but you didn't stop there did you? My "three" word note must have carried more weight than even I thought it might. Forgive me but even as I read your article I had a feeling that there was content added or clarified with me in mind, funny eh? You know I like you and read your missives, and while your specialty may not have too much "guess work" in it...the only "really clear" thing within the findings is that the fossil is inconclusive as anything transitional. Now if they found a couple hundred thousand examples that might be more interesting, but 2.5 examples is clearly isolated. To be honest with you Michael I really think the fossil record across the board is a bigger tease than anything else...always tantilizing but never conclusive.

    adaptivecomplexity
    I'm not touchy, I just find that the God of the Gaps view you espouse is amazingly ridiculous.

    What is your alternate explanation for the whale fossil series? That the Designer just poofed up some amphibious mammals with some skeletal traits of today's whales, let them go extinct, and then poofed into existence a few species that look a little more like today's whales, and so on, until finally "designing" modern whales?

    You remind me of David Berlinski, the ID advocate in the Firing Line debate I embedded in a post last week. When faced with the clear fossil series showing a transition from reptiles to mammals, hiw response was basically, "what about the insects?" So mammals evolved from reptiles, but God designed the insects?

    ID believers never, ever get specific. If you think you can come up with a detailed, alternate explanation for the fossils discussed here, be my guest. You ID people don't need "a couple hundred thousand examples", because you can't even explain the numerous examples we have.  Until you ID people do that, you should drop the pose of fake skepticism and just admit that it's really wilful ignorance.

    And BTW, you seem to be confused about protocetids - there are more than "2.5 examples" of fossil amphibious mammals.
    Mike
    Steve Davis
    A reasonable guess, Perry, is one based on evidence, as the article clearly stated. This is how science progresses. It's the reason you can sit at your computer and indulge your "wilful ignorance."
    ....Hank....when you add "reasonable guessing" to next years list, Michael and now also confirmed by Steve, you should also add "willful ignorance"...wow we are off to a strong start in 2009.

    adaptivecomplexity
    Willful ignorance or honest skepticism?

    BERLIN – A bishop who faces a Vatican demand to recant his denial of the Holocaust said he would correct himself if he is satisfied by the evidence, but insisted that examining it "will take time," a German magazine reported Saturday.

    Richard Williamson is one of four bishops from the ultraconservative Society of St. Pius X whose excommunication was lifted by the Vatican last month. The decision sparked outrage because Williamson had said in a television interview he did not believe any Jews were gassed during the Holocaust.

    "Since I see that there are many honest and intelligent people who think differently, I must look again at the historical evidence," the British bishop was quoted as saying.

    "It is about historical evidence, not about emotions," he added, according to the report. "And if I find this evidence, I will correct myself. But that will take time."

    "I was convinced that my comments were right on the basis of my research in the '80s," Der Spiegel quoted Williamson as saying. "I must now examine everything again and look at the evidence."

    Somehow I doubt that there is any evidence out there that will change his mind. Evolution deniers may not be in the same moral category as Holocaust deniers, but the intellectual pose is the same.
    Mike
    Hank
    Right.  For people with an ideological agenda, every science will have flaws.    People who want to be convinced the LHC will open up a black hole and doom us can point to infinite possibilities to rationalize their doubt.   People who want to believe the world will end in 2012 thanks to Mayans will believe it until January 2013, I guess.  

    Likewise there can never be evidence for evolution if creationists insist it was all planted.   What would make it fun is someone who insists it was planted by Mayans using the LHC to go back and forth in time.    That would be awesome.

    We just never take evolution deniers too seriously because we're in science and not in the culture wars (though someone has to be, so we are glad other people do it) and we recognize that biology lends itself to doubt without any real recourse - it's not like people will unevolve if they don't accept evolution.   If they don't accept gravity, though, they end up being a gooey mass on the sidewalk.    So physicists tend to laugh off skeptics about gravity.
    ...Hank, I don't think the World will end on 2012, but I suspect it will end when folks least expect it to, and if the World itself does not end the end will come in a more personal way to the scoffer. Thanks for revealing the exact same feeling that I have in regards to evolutionary scientists as we do not put much stock in the fantasy pathway that even their cohorts find little to agree upon. No one has to "accept" ??? gravity, but all do acknowledge it's existance (who doesn't believe in gravity?? outside of a few folks who still shrink heads and wear plants for clothes). Why is an animal that has become extinct in the recent past (and present) any different than one from the distant past? Many birds and other animals have dissappeared from view forever but what does that prove? Nothing, and the death and extinction of ancient animals does not confirm evolution only the death of a single example of whatever it is. Science has flaws irregardless of idiological adjenda...so what? Are you saying that there are zero evolutionary scientists or those who believe in the boondoggle that do not have an adjenda as well?? come on...

    Hank
    I use the word 'accept' rather than 'belief' because belief is a social/religious/subjective construct and scientific acceptance is a data-driven one.    It is completely outside my interest whether or not anyone believes evolution is the source of life in the universe or anywhere else - but refusing to accept that evolution has occurred is outside any reasonable science discussion.  
    ...of course you being the arbiter of all things "reasonable" I would guess?? Interesting but predictable that you think only those who embrace those things that "you accept" as reasonable would be able to participate in a science discussion. "Uhhh...Mr. Newton...sorry but you can't sit here with Hank and Michael, they can't accept your way of thinking. By the way...I've never asked but can you clarify where you stand on the existance of the Almighty??...just for the record.

    Hank
    You're comparing yourself to Newton?

    It's unlikely that Newton would deny evolution given all the evidence and he most certainly believed in God.   Francis Collins believes in God yet is one of the most prominent biologists in the world and obviously accepts evolution.

    You have a penchant for exaggeration and hyperbole about this but there isn't much need for it.  No one criticizes you for believing in God - that's the whole point of faith - but denying evolution in a science community is no different than denying gravity.
    adaptivecomplexity
    "Uhhh...Mr. Newton...sorry but you can't sit here with Hank and Michael, they can't accept your way of thinking.
    Newton put his money where his mouth was and actually did some real science.
    Mike
    adaptivecomplexity
    Many birds and other animals have dissappeared from view forever but
    what does that prove? Nothing, and the death and extinction of ancient
    animals does not confirm evolution only the death of a single example
    of whatever it is.
    This is a prime example of how creationists can look at all of the dots and refuse to connect them. It's like saying that, just because we can observe erosion caused by the Colorado river in the Grand Canyon today, we have no right to infer that the canyon was produced by erosion over millions of years.

    How about this Perry - do you really think that scientists were not entitled to accept the existence of atoms until we developed the technology to observe atoms "directly"? Because that's what you imply with your reasoning. 'Direct eyewitness evidence' only takes you so far when you're talking about events that take place on extremes of spatial and time scales. But it doesn't mean that the non-eyewitness evidence is any less substantial, and in fact, eyewitness evidence itself can be deceptive.
    Mike
    Nice dodge, but you know exactly what I was refering to, your analogy was asinine and beneath you. Are you an expert in the field of fossils? Is that your chosen field of study and research? What do you think the odds are that some land mammal would constantly pursue a significant environmental change and then what would have to be multiple millions of "positive, beneficial mutations to accomodate just the single movement of a nostril to become a blow hole? Now do it all over again because you will need a mate changing the exact same way independently to be compatable. Now I sure hope that every time reproduction kicks in that the first million or two potential offspring can survive because if not then it's all a moot point now isn't it. What Hank and you "accept" is simply the most preposterous, and "faith" based belief that has ever been perpetrated on the general public. The reason is not the persuit of Science, it is clearly because the alturnative is simply not permissable. We are not proving erosion and to be honest the Colorado River is doing very little in the way of erosion any more as the canyon walls are some 400 feet about the river bed. The Mt. St Helens erruption and the following aftermath of Spirit Lake easily show how significant amounts of identical erosion characteristics can happen in hours and days much less multiple millions of years. You "must" lean on massive amounts of time as a crutch to explain away the impossible...the more time the more possible. This is what motivates Gerhard as well. The "impossible" can not be "possible" because the alturnative is simply not permissable. If you want to hang your hat on atoms that can't be seen I'm ok with that, I know that you already do this, but you would deny me the equal right to hang my hat on something that can't be seen as well and have the additional insult that what I can't see is somehow "less" intelligent that what "you" can't see. That sounds rather hypocritical don't you think?

    adaptivecomplexity
    Talk about pot calling the kettle black. You call my statement a dodge and yet you're completely unwilling to offer your own 'design-based' explanation for the extensive series of fossils that shows gradual changes over time from a land mammal, to an amphibious mammal, to whale-like creatures with tiny legs, to modern whales.

    What do you think the odds are that some land mammal would constantly
    pursue a significant environmental change and then what would have to
    be multiple millions of "positive, beneficial mutations to accomodate
    just the single movement of a nostril to become a blow hole?
    This statement demonstrates your complete cluelessness regarding genetics and developmental biology. One of the most amazing discoveries of the field called evo-devo is that you don't need "millions of positive beneficial mutations" to achieve something like the shift from a nostril to a blow hole. A few mutations suffice for significant developmental changes - something we can demonstrate in the lab, maybe not with whales (because they're obviously impractical to work with) but with insects and vertebrates like skates and rays.

     And again, what's your explanation for the intermediate nostril-blowholes we see in the fossil record?

    The Mt. St Helens erruption and the following aftermath of Spirit Lake
    easily show how significant amounts of identical erosion
    characteristics can happen in hours and days much less multiple
    millions of years.
    Again, you're clueless about geology. There very definitive differences between the signature of volcano-induced erosion and more gradual erosion. They are not identical. They may in some cases produce similar large scale effects, but you can see the differences in the rocks.

    Instead of repeatedly demonstrating your complete lack of knowledge about the relevant fields, why don't you put your money where your mouth is and give us a reasonable, scientific explanation for the whale fossil series that doesn't involve evolution. All we ever get from creationists is an argment from personal incredulity, and never a coherent, self-consistent explanation for what's observed out in nature.
    Mike
    ...the reference to the dodge was in regards to your questionable analogy/use of the holocaust the first time and the step around of it in my second post...nothing more. I like the clueless observation you pose as you have positioned yourself right along with the rest of the elitists as you "know" it all and we are fools. It is rather stereotypical of the Biology bunch in particular. But not so fast with the wave of your hand as you stand behind a "few" mutations changing a blow hole, can you equally stand behind "everything" happening this way? I may be clueless about many things but you are a snake oil salesman with the stuff you postulate. I say that there is zero transitioning between any of these animals, that they are/were whole and complete in their intended design and their offspring are the representative of it's parents not some "positive mutation" on it's way to something else. I can imagine what goes on in some of these labs you operate in, but tell me how does information get "added" to something when 99
    % of mutations are inclined to "lose" information which is contrary to moving forward and leads to a weaker example with less likelyhood of survival.

    Your 8th grade explanation of the differences in erosion between an eruption and water flow doesn't say much for your current understanding of erosion as you do not need to be a geologist to see what has happened. As you have so many times opined that there is no plausible answer outside of evolution, even with the book knowledge you have strived for over the years there is no difference between the incredulity I have for your explanations as you have for mine the difference is apparent. I do not have to change my origins, whereas you can't agree on one. You can't see the forest for the trees Michael. You also demonstrate your complete lack of knowledge as well but one day you will know..eh?

    adaptivecomplexity
    Likewise there can never be evidence for evolution if creationists insist it was all planted.   What would make it fun is someone who insists it was planted by Mayans using the LHC to go back and forth in time.    That would be awesome.
    Now there is an ideological agenda I can buy into!
    Mike
    ...well I didn't think it possible but you have done it . This last post from you of course confirms nothing scientific only that you are an ass by posting it. Something that happened in the last 65 years in clear Public view with "eye witnessess" and pictographic evedence not to mention "survivors testimony" you can somehow correlate into an argument against someone who doesn't hold fast to your view of the past. Congratulations Michael...you and Steve can hold hands now...

    Please allow me to deal with some of the creationist arguments.

    Lets see.........Colorado river IS still eroding, hell it's a brown river.....lots of eroded stuff. Incidentally what do the cliffs above have anything to do with it other than where the river has already eroded the STONE? Likewise, comparing stone with volcanic ash and dirt doesn't exactly work.

    How does the movement of a nostril require millions of genetic mutations? It doesn't need any mutations. All it needs is for the HOX gene coding nostril placement to place it there. With the alternative transcription sites, transposons, viral interactions, the multiple mutations, etc that isn't an illogical assumption.

    Why does a single organism have to have be blessed with a million mutations and then find another "toxic waste avenger" to mate with? A secluded POPULATION that has sex while under selective pressure is plenty.

    We can't exactly see atoms. you are right........We can smash 'em together though!!!

    Now lets get PERSONAL!!! All powerful all knowing god........had to rest?

    ok ok wait. The FIRST monotheistic religion was initiated by Akhenaten before moses existed. Outside of the bible there is no proof of Moses. No mention of a pharoah- eating ocean, no mention of plagues, no Jew strike, no hopped up Hebrews running around the desert seeing god.....nothing. To make matters worse, the Hebrews played a nice game of telephone, in ancient Hebrew of course. They wrote everything over an 800 year period, Then lost it. Convenient.

    How about Jesus? Do you like your "false idol"? Well, again, outside of the bible there is no mention of a miraculous virgin popping out babies who can feed the planet with fish food, cure deadly diseases, create zombies, become a zombie, or any of the other shennanigans . What there IS proof of is old myths of Dionysius, Osiris, Mithras, Buddha, Krishna, and several others who ALSO performed the exact same miracles. Lying momma and all.

    Along comes the never ending game of Hebrew telephone with newly created texts!! in Greek. Then latin, Then old english. Then autocracy promoting propaganda like the KJV paid for by your local king to prove divine origins.

    This is the alternative to rock solid investigatory science? Some fake Egyptian religion played by illiterate lost drugged Jews who stole other religions, then mistranslated several times, on purpose even!!!

    No thanks. I'll stick with "The Flying Spaghetti Monster" thankyou

    logicman
    As a thinker, it is incumbent on me to seek out evidence to support any claim made by those who wish to do my thinking for me. I have no problem reconciling my personal religeous beliefs with my acceptance of evolution as a proven fact. I might have trouble if I followed doctrinaire policy, but I am neither a follower nor a leader. I am a thinker - sum ergo cogito, as one might say. The King James Bible, for all that it was 'authorised' by the establishment, for all its errors of translation, made a major contribution to the development of the English language. It also gave any averagely literate person the opportunity to see at first hand whether or not the bible actually said what some preacher claimed that it said. Literacy levels in England rose sharply after the KJ Bible was published. Concurrently, church attendance levels could only be maintained by the imposition of fines on non-attendees. There may be a connection here with the rise in scientific literacy. ;) When anybody tells me that x, y or z is the case, I tend to check for myself. Re:"outside of the bible there is no mention of a miraculous virgin" Fact: the Quran describes Mary as a virgin and chapter 12 of the Quran is named Mirriam (Mary). The Quran also was responsible for a rise in literacy, and especially scientific literacy. Never forget the muslim world's contribution to science, art, architecture etc. As to intelligent design: the human eye, which is blinded by snow or sand and which cannot see clearly underwater is the product of an intelligent design? You're joshing me, right? A design is a map, plan, blueprint or even a mathematical formula. Could an intelligent designer, if such exists, not have just designed a handful of laws of nature? When filling a glass you don't need to inspect and position every single particle. You just pour, and then let the laws of gravity do the rest.
    DISCLAIMER: Trust me, I am one of the most accepting people in the world. I DO react when people attempt to impose their cop out on my proof. Most of my friends are christian, some fundamentalist, we just agree to disagree.

    I agree with the Quran claiming the virgin birth of Jesus. The Quran is based on the bible =same source. Also, this does not avoid the fact that every single miracle claimed for Jesus was performed several times prior to his birth by other "deities".

    I don't think the KJV helped literacy at all. The printing press maybe.

    I honestly have no idea if the Q'uran helped middle east literacy. I doubt it, but that is something I will check up on.

    The fact that the islamic world is responsible for a good portion of early science, politics, philosophy, etc is one of my favorite comments to the Wedge document.

    Dear Sir
    I heart the whale month some time will come got stone, do you have the picture to show how the stone look like? is the a value? where to find them or to see them?Thanks

    Regard
    Jill