Scientists find missing link between whale and its closest relative, the hippo

UC Berkeley News ^ | 24 January 2005 | Robert Sanders, Media Relations

[PatrickHenry]

A group of four-footed mammals that flourished worldwide for 40 million years and then died out in the ice ages is the missing link between the whale and its not-so-obvious nearest relative, the hippopotamus.

The conclusion by University of California, Berkeley, post-doctoral fellow Jean-Renaud Boisserie and his French colleagues finally puts to rest the long-standing notion that the hippo is actually related to the pig or to its close relative, the South American peccary. In doing so, the finding reconciles the fossil record with the 20-year-old claim that molecular evidence points to the whale as the closest relative of the hippo.

"The problem with hippos is, if you look at the general shape of the animal it could be related to horses, as the ancient Greeks thought, or pigs, as modern scientists thought, while molecular phylogeny shows a close relationship with whales," said Boisserie. "But cetaceans – whales, porpoises and dolphins – don't look anything like hippos. There is a 40-million-year gap between fossils of early cetaceans and early hippos."

In a paper appearing this week in the Online Early Edition of the Proceedings of the National Academy of Sciences, Boisserie and colleagues Michel Brunet and Fabrice Lihoreau fill in this gap by proposing that whales and hippos had a common water-loving ancestor 50 to 60 million years ago that evolved and split into two groups: the early cetaceans, which eventually spurned land altogether and became totally aquatic; and a large and diverse group of four-legged beasts called anthracotheres. The pig-like anthracotheres, which blossomed over a 40-million-year period into at least 37 distinct genera on all continents except Oceania and South America, died out less than 2 and a half million years ago, leaving only one descendent: the hippopotamus.

This proposal places whales squarely within the large group of cloven-hoofed mammals (even-toed ungulates) known collectively as the Artiodactyla – the group that includes cows, pigs, sheep, antelopes, camels, giraffes and most of the large land animals. Rather than separating whales from the rest of the mammals, the new study supports a 1997 proposal to place the legless whales and dolphins together with the cloven-hoofed mammals in a group named Cetartiodactyla.

"Our study shows that these groups are not as unrelated as thought by morphologists," Boisserie said, referring to scientists who classify organisms based on their physical characteristics or morphology. "Cetaceans are artiodactyls, but very derived artiodactyls."

The origin of hippos has been debated vociferously for nearly 200 years, ever since the animals were rediscovered by pioneering French paleontologist Georges Cuvier and others. Their conclusion that hippos are closely related to pigs and peccaries was based primarily on their interpretation of the ridges on the molars of these species, Boisserie said.

"In this particular case, you can't really rely on the dentition, however," Boisserie said. "Teeth are the best preserved and most numerous fossils, and analysis of teeth is very important in paleontology, but they are subject to lots of environmental processes and can quickly adapt to the outside world. So, most characteristics are not dependable indications of relationships between major groups of mammals. Teeth are not as reliable as people thought."

As scientists found more fossils of early hippos and anthracotheres, a competing hypothesis roiled the waters: that hippos are descendents of the anthracotheres.

All this was thrown into disarray in 1985 when UC Berkeley's Vincent Sarich, a pioneer of the field of molecular evolution and now a professor emeritus of anthropology, analyzed blood proteins and saw a close relationship between hippos and whales. A subsequent analysis of mitochondrial, nuclear and ribosomal DNA only solidified this relationship.

Though most biologists now agree that whales and hippos are first cousins, they continue to clash over how whales and hippos are related, and where they belong within the even-toed ungulates, the artiodactyls. A major roadblock to linking whales with hippos was the lack of any fossils that appeared intermediate between the two. In fact, it was a bit embarrassing for paleontologists because the claimed link between the two would mean that one of the major radiations of mammals – the one that led to cetaceans, which represent the most successful re-adaptation to life in water – had an origin deeply nested within the artiodactyls, and that morphologists had failed to recognize it.

This new analysis finally brings the fossil evidence into accord with the molecular data, showing that whales and hippos indeed are one another's closest relatives.

"This work provides another important step for the reconciliation between molecular- and morphology-based phylogenies, and indicates new tracks for research on emergence of cetaceans," Boisserie said.

Boisserie became a hippo specialist while digging with Brunet for early human ancestors in the African republic of Chad. Most hominid fossils earlier than about 2 million years ago are found in association with hippo fossils, implying that they lived in the same biotopes and that hippos later became a source of food for our distant ancestors. Hippos first developed in Africa 16 million years ago and exploded in number around 8 million years ago, Boisserie said.

Now a post-doctoral fellow in the Human Evolution Research Center run by integrative biology professor Tim White at UC Berkeley, Boisserie decided to attempt a resolution of the conflict between the molecular data and the fossil record. New whale fossils discovered in Pakistan in 2001, some of which have limb characteristics similar to artiodactyls, drew a more certain link between whales and artiodactyls. Boisserie and his colleagues conducted a phylogenetic analysis of new and previous hippo, whale and anthracothere fossils and were able to argue persuasively that anthracotheres are the missing link between hippos and cetaceans.

While the common ancestor of cetaceans and anthracotheres probably wasn't fully aquatic, it likely lived around water, he said. And while many anthracotheres appear to have been adapted to life in water, all of the youngest fossils of anthracotheres, hippos and cetaceans are aquatic or semi-aquatic.

"Our study is the most complete to date, including lots of different taxa and a lot of new characteristics," Boisserie said. "Our results are very robust and a good alternative to our findings is still to be formulated."

Brunet is associated with the Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine at the Université de Poitiers and with the Collège de France in Paris. Lihoreau is a post-doctoral fellow in the Département de Paléontologie of the Université de N'Djaména in Chad.

The work was supported in part by the Mission Paléoanthropologique Franco-Tchadienne, which is co-directed by Brunet and Patrick Vignaud of the Université de Poitiers, and in part by funds to Boisserie from the Fondation Fyssen, the French Ministère des Affaires Etrangères and the National Science Foundation's Revealing Hominid Origins Initiative, which is co-directed by Tim White and Clark Howell of UC Berkeley.

[King Prout]

survey sez: XXX

try again.

I have already explained that evolutionary theory has been confirmed as a predictor of data not available when the theory was coined. THAT IS A STANDARD TEST OF A THEORY IN THE SCIENTIFIC METHOD.

Clearly, this is not enough FOR YOU.

So, cough it up, ducky: EXACTLY WHAT DATA SET DO YOU REQUIRE TO SATISFY YOUR DEFINITION OF "PROOF"???

[Jaysun]

Mendel's pea experiments illustrate alleles. You might have white flowers or yellow flowers. One might be dominate and the other recessive. This gives rise to hybrids. A mutation might occur that makes a red flower. Then there is a third allele.

I've heard about the kinds of changes that you're describing and I think they're amazing. However, changing the color of a flower under unnatural circumstances is a far cry from sprouting eyeballs, legs, and wings in the wild (regardless of time). It's still a flower, that's all I'm saying.
Bed sounds like a good idea. See ya later.

[King Prout]

Ha!

LAST POST!

It's a UT thing... you wouldn't understand.

[Jaysun]

This is where you're mistaken. With computerized DNA sequencing technology, bacteria genomes can be assembled in a matter of weeks and compared with other previously assembled genomes within hours. Bacteria are relatively simple organisms, their DNA has been well-studied and their life cycles are well known. Cultures of bacteria are first sequenced and then exposed to a set of stressful environmental conditions. After the experiments are complete, DNA samples are taken from the surviving bacteria, run through the sequencing machines, and compared with that of their ancestors. From these experiments, the rate of change in bacteria DNA is objectively measured. From these experiments, predictions may be made and conclusions can be reached about if, or how far a certain trait might progress through several generations. The results are predictable and repeatable.

Splendid! Thanks for dishing up the first straight answer I've gotten all day. Can you tell me where or how I can gain access to some data on this? I'd like to check into this further.

[Jaysun]

When did whales stop breathing air? ;)

For some it was when they became redwood trees, for others it was merely a reaction to the shock of seeing yourself in the mirror for the first time and noticing that you've got legs hanging off of your stomach.

No, I made a mistake when posting that this morning. Too much wine for breakfast I suppose.

[Jaysun]

King Prout,
This will mark my place for the night. I'll extend the courtesy of responding to your nauseating prattle in the morning.

We should remember that we're all on the same team here and that we just happen to disagree on an issue. People disagree with me all the time, which simply means that they're wrong, and I can't hold ignorance against them. ;o)

I hope I didn't offend tonight. Many of my crude remarks were a poor attempt at humor on my part. The fact that I've been delirious from lack of sleep in the last two days may have also played a role.

I'll talk with you later. Sleep well monkeys.

[Liberal Classic]

Please understand that I am not a biologist, but a computer technologist. That having been said, the fields in question are called bioinformatics and comparitive genomics. They are relatively new fields of study, only recently made possible from advances in computerization.

Good websites to start reading about bioinformatics are the Washington University (St Louis Missouri) School of Medicine Genome Sequencing Center and Baylor College of Medicine (Houston Texas) Human Genome Sequencing Center. Both sites have pages documenting research projects on microbial genomes, as well as those of macroscopic creatures ranging from the humble fruit fly to the well known Human Genome Project. I honestly admit much of what is written on these pages is largely beyond my level of biological understanding. However, it is my understanding that microbial genomes, as some of the smallest and easiest to work with, have been studied the longest. For comparison, to fully sequence a mammalian genome still takes several years and is a complex undertaking, whereas viral genomes can be sequenced in a day. These websites deal mostly with getting the DNA sequences into computer readable formats, but from these pages are links to other research projects and educational institutions doing this type of research. For general reading just type "bacterial genome" or "comparitive genomics" or "bioinformatics" or "molecular genetics" into a search engine and start clicking.

[Stultis]

These statements are not irrrelevant at all, they are truth.

Race, Buddy, are you even trying to follow the conversation? I didn't say they were globally irrelevant. I said they were irrelevant to the issue I happened to be discussing when you replied, which was the prevailing views among Christians about the age of the earth and "flood geology" since the advent of modern geological science. Geology began to take shape as a scientific discipline early in the 19th Century. Your quotes were from the early part of the millennium!

BTW, was it also "truth" when Theophilus, who you cited, claimed that the heavens were a solid dome covering the (by implication flat) earth?

In fact, the abandonement of these doctrines about 100 years ago WAS A NEW THING and very short lived until RA TORREY'S "THE FUNDMENTALS" came out.

Guess what, Race, I've actually read The Fundamentals (at least the articles therein that address scientific issues) but it seems that you haven't. If you did you'd know that not one of the articles takes a young earth position, nor adopts "flood geology," but instead affirm or accept the findings of geological science that the earth is ancient. What's more, none of articles that discuss it unreservedly rejects evolution, instead adopting views ranging from acceptance, to neutrality to mild skepticism.

Are you finally done pontificating on matters you don't know a damn thing about? (Never mind. I know the answer to that from experience.)

[AntiGuv]

To quote the source that you cited, Wikipedia: "A group of organisms is said to have common descent if they have a common ancestor. In biology, the theory of universal common descent proposes that all organisms on Earth are descended from a common ancestor or ancestral gene pool.¹" (bold emphasis added). To wit:

"¹ The earliest life-like forms probably exchanged genetic material laterally in a manner that is analogous to lateral gene transfer amongst bacteria. For this and other reasons, the most recent common ancestor may have been a genetic pool rather than an organism."

In fact, I personally think that if abiogenesis is the ultimate origin of life on earth, then it is far more probable that the universal common ancestor is a gene pool rather than one individual organism that preempted all others (though the latter would hardly contravene the precept of abiogenesis either, much less the underpinnings of evolution). If instead some kind of deity were the first cause of terrestrial evolutionary development then it would be more efficient to just design the first, solitary replicating organism - since it would already contain all the necessary ingredients for everything that followed.

Leaving that aside, this was your initial question and my response:

Are you saying that it is possible all life may not have a common ancestor?

That is certainly possible and would not contravene the scientific underpinnings of evolution in the slightest.

Although we have no evidence of this and it appears fairly unlikely at this juncture, it is also possible that we have not yet discovered the extant remnant, if it exists, of any organisms that have descended from a different common ancestry than that of all known forms of terrestrial life. So, whereas we don't have any evidence of this, it is also possible that it's out there but we just haven't uncovered it, and if we did uncover it then it would definitely not contravene the scientific underpinnings of evolution in the slightest (but it would be a most fascinating subject for research!) any more so than discovering life on Europa or Titan would.

Speaking of which, another reason your statement is certainly possible is because you didn't specify all life on earth, but I knew that's what you meant and answered accordingly. If you had asked about "common ancestry" rather than a "common ancestor" then I would've said: There is no evidence or any reason to believe that any known life on earth originated apart from and outside of the common lineage.

[Stultis]

Oooops. Should have said:

Your quotes were from the early part of the previous millennium!

[Stultis]

Partial retraction. There apparently were a couple anti-evolution articles in The Fundamentals, according to a secondary source I just found. I don't remember them, so I'm guessing for the moment they weren't articles that were primarily addressing scientific issues. Or maybe the edition I have doesn't include all the later articles? (It's only 5 volumes, I think, but possibly it doesn't follow the breakdown of the original. It's packed away right now.) Or maybe I just forgot.

By the way, while I remembered Orr and Wright, I'd forgotten that your hero Torrey was one of those who contributed an article that was open to evolution! Anyway, here's what I found:

http://www.talkorigins.org/faqs/ce/2/part12.html

Many evangelical Christians today suppose that Bible believers have always been in favor of a "young-universe" and "creationism." However, as any student of the history of geology (and religion) knows, by the 1850s all competent evangelical Christian geologists agreed that the earth must be extremely old, and that geological investigations did not support that the Flood "in the days of Noah" literally "covered the whole earth." Rev. William Buckland (head of geology at Oxford), Rev. Adam Sedgwick (head of geology at Cambridge), Rev. Edward Hitchcock (who taught natural theology and geology at Amherst College, Massachusetts), John Pye Smith (head of Homerton Divinity College), Hugh Miller (self taught geologist, and editor of the Free Church of Scotland's newspaper), and Sir John William Dawson (geologist and paleontologist, a Presbyterian brought up in a fundamentalist atmosphere, who also became the only person ever to serve as president of three of the most prestigious geological organizations of Britain and America), all rejected the "Genesis Flood" as an explanation of the geologic record (or any part of that record), and argued that it must have taken a very long time to form the various geologic layers. Neither were their conclusions based on a subconscious desire to support "evolution," since none of the above evangelical Christians were evolutionists, and the earliest works of each of them were composed before Darwin's Origin of Species was published. The plain facts of geology led them to acknowledge the vast antiquity of the earth. And this was before the advent of radiometric dating.

By the very early 1900s, even conservative theologians at Princeton Theological Seminary were prepared in varying degrees to concede to science a long earth history, the transmutation of species by evolution, and even an evolutionary past for the human physical form. Such theologians included B. B. Plarfield, the famous inerrantist Presbyterian, who at that time oversaw the publication of the Princeton Theological Review.

Even when the twelve-volume paperback series, The Fundamentals, was published between 1910 and 1915 (an interdenominational work that launched this century's "fundamentalist" movement), it contained cautiously pro-evolution stances of conservative Christian theologians like George Frederick Wright, James Orr, and R. A. Torrey. It was only in the eighth collection of Fundamentals papers that this cautious advocacy of evolution was matched by two decisively and aggressively anti-Darwin statements, one by someone who remained anonymous and another by the relatively unknown Henry Beach, both of whom lacked the theological and scientific standing of the senior evangelicals already mentioned.

I still think I'm correct in saying that NONE of the articles take a young earth view.

[Stultis]

Here's a bit more (empahsis added):

http://www.pbs.org/wgbh/evolution/religion/revolution/1910.html

c. 1913: Flood Geology
(Evolution Challenged)

Flood geology has few proponents. Many, if not most, conservative Christians of the day accept that Earth may be millions of years old. Yet the seeds for the young-Earth creationist movement are sown. A Seventh-day Adventist named George McCready Price, in his book The Fundamentals of Geology, argues that virtually all fossil-bearing rock on Earth can be attributed to the one year of Noah's flood. This idea will not be widely accepted by fundamentalists for 50 years.

[Stultis]

The "wolphin" is the fertile offspring of a bottlenose dolphin and a false killer whale (which are different species from each other). This wolphin mated with a dolphin and produced a live baby. Kind of breaks the "absolute requirement" for differentiating species. :-)

Not necessarily. The biological species concept is based on the criteria that populations don't interbreed in the wild. It doesn't require that distinct species are biologically incapable of hybridizing, but just that they do not in fact do so in nature (or do so with a low enough frequency that the populations still remain effectively isolated, i.e. rarely enough that it doesn't matter).

Animals like these marine mammals kept in captivity may behave very differently than in the open ocean. The article doesn't give any details. Maybe there were just one or a few false killer whales. They were apparently kept with the porpoises and therefore may have behaved as members of the porpoise herd. They may have thereby learned and adopted behaviors they wouldn't in the wild. It's likely that normal behaviors, geographical or ecological distribution, and the like, would prevent this from happening in nature.

[jennyp]

I always learn something new from you!

[Stultis]

Could you please provide us with the source of your list? Thanks.

The following is a partial list of people who were both scientists and creationists.

There are numerous problems with this list. At least if we assume that "creationists" are meant to be understood as "antievolutionists". (Of course most evolutionists are also creationists, in that most believe in God and embrace some kind of creation doctrine. This is no surprise if we bear in mind the around 90 percent of the population are theists of some sort, and well over half are evolutionists of some sort.)

I'll ignore the pre-Darwin portion of the list, because that's just silly. From the "Just After Darwin" portion, the following are ones that I happen to know, just off the top of my head, were either outright evolutionists or open to evolution:

Matthew Maury
James Dana
John William Dawson
William Thompson, Lord Kelvin

I'm pretty certain there are others erroneously included. Some of these inclusions are really inexcusable. Dana, for instance, was famously cited as an anti-evolutionist in his lifetime and wrote to the magazine to correct this. After a hundred and twenty five years you guys should be able to get this stuff right.

Both of you tell me with a straight face that these scientists are "quacks" and non-scientists.

Most aren't, but at least one or two are. I don't know a great deal about Charles Piazzi Smyth ("Astronomy" in "Just After Darwin"). Maybe he was a decent astronomer, but he engaged in quackery in his role as a founder of "pyramidology". In the modern period Clifford Burdick "Geologist" never obtained a genuine graduate (let alone advanced) degree, passed off phoney credentials at various times, and was widely considered a doofus even by fellow creationists.

[muir_redwoods]

Pakicetus is the "missing link" or intermediate species fossil between land animals and modern whales and dolphins. Google is a search engine that even children know how to use to find things on the web. I'm not surprised that both are mysteries to you.

[HankReardon]

What is a some people on here? They exercise "courage" to talk down to people they would never have in real life? I went to search engine and read about the discovered bones. Bones are something left behind one an animal dies, decays last. Behind is what you you kiss!

[HankReardon]

Yes, "species" is a category made up by mankind to help divide the animal and plant kingdom into groups to enable study. The distinguishness of species is determined by man, subject to change.

[Junior]

A "Fundamental" placemarker.

[HankReardon]

I love watching that show "Cops" it shows the "species" which has attained the top rung of the evolutionary ladder very well. Or "Jerry Springer", examples of the success of evolution. I think I'll go discover some laws of physics today, afterall, I am 300 years more evolutionarily advanced than Isaac Newton. Should be easier for me.

Okay, spelling seems good, grammar, not so sure about. Please be gracious enough to forgive any errors that would get by a person of such a bourgeois station.