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Evolution rewritten, over and over

Aug. 31, 2010
Courtesy of the University of Bristol
and World Science staff

Palaeon­tol­o­gists are always claim­ing that their lat­est fos­sil dis­cov­ery will “rewrite ev­o­lu­tion­ary his­to­ry.” 

Is this just boast­ing, or is our knowl­edge of ev­o­lu­tion so fee­ble that it changes eve­ry time we find a new fos­sil?

A team of scientists at the Uni­vers­ity of Bris­tol, U.K. de­cid­ed to find out, through in­ves­ti­ga­t­ions of di­no­saur and hu­man ev­o­lu­tion. Their stu­dy, pub­lished this week in the re­search jour­nal Pro­ceed­ings of the Roy­al So­ci­e­ty B, sug­gests most fos­sil dis­cov­er­ies don’t make a huge dif­fer­ence: they con­firm, rath­er than con­tra­dict our un­der­stand­ing of ev­o­lu­tion­ary his­to­ry.

Bi­ol­o­gists or­gan­ize life forms in­to ev­o­lu­tionary or "family" trees si­m­i­lar to the ones above, al­though many de­tails are un­der con­stant de­bate. The "tree of life" above is di­vid­ed in­to two parts. A big-picture view, top, shows the three ma­jor "domains" of life, two of which con­sist sole­ly of one-celled or­gan­isms. Be­low the hor­i­zon­tal line is a more de­tailed view of the sub­di­vi­sion Eu­karya, which in­cludes hu­mans and oth­er multi-cellular or­gan­isms along with many ad­di­tion­al one-celled or­gan­isms. (Im­age cour­tesy Nat'l Inst. of Health)


This is es­pe­cially true of the fos­sil rec­ord of hu­man ori­gins from their mon­key rel­a­tives, the in­ves­ti­ga­tors found. Though early hu­man fos­sils are very rare, and new dis­cov­er­ies make a big splash in the sci­en­tif­ic lit­er­a­ture and in the me­dia, they sit ran­domly across the ev­o­lu­tion­ary tree of early hu­mans. 

In oth­er words, the re­search­ers said, most dis­cov­er­ies of new fos­sil spe­cies simply fill in gaps in the fos­sil rec­ord that we al­ready knew ex­isted.

“Hu­man fos­sils are very rare, and they are costly to re­cov­er be­cause of the time in­volved and their of­ten re­mote loca­t­ions. Sci­en­tists may be pushed by their spon­sors, or by news re­porters, to ex­ag­ger­ate the im­por­tance of their new find and make claims that ‘this new spe­cies com­pletely changes our un­der­stand­ing,’” said James Tarver, lead­er of the stu­dy.

The sto­ry of di­no­saur ev­o­lu­tion is a bit more com­pli­cat­ed, he added. 

New di­no­saur fos­sils are be­ing found in places around the world where they’ve nev­er been looked for be­fore, such as Chi­na, South Amer­i­ca and Aus­tral­ia. These fos­sils, the sci­en­tists said, are fun­da­men­tally chal­leng­ing ex­ist­ing ideas about di­no­saur ev­o­lu­tion. But this seems to tell us that there are still many new spe­cies of di­no­saurs out there in the rocks.

“These are im­por­tant re­sults,” said Mi­chael Ben­ton, anoth­er mem­ber of the team. “It might seem neg­a­tive to say that new finds do, or do not, change our views. How­ev­er, to find that they don’t means that we may be close to satura­t­ion in some ar­eas, mean­ing we know enough of the fos­sil rec­ord in some cases to have a pret­ty good un­der­stand­ing of that part of the ev­o­lu­tion­ary tree.”

“We can use these stud­ies as a way of tar­get­ing new ex­pe­di­tions,” added co-author Phil Dono­ghue. “If di­no­saurs are poorly un­der­stood from a par­tic­u­lar part of the world, or if some oth­er group is al­to­geth­er incom­pletely known, that’s where we need to de­vote great­er ef­forts.”


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Palaeontologists are forever claiming that their latest fossil discovery will “rewrite evolutionary history.” Is this just boasting, or is our “knowledge” of evolution so feeble that it changes every time we find a new fossil? A team of researchers at the University of Bristol, U.K. decided to find out, through investigations of dinosaur and human evolution. Their study, published this week in the research journal Proceedings of the Royal Society B, suggests most fossil discoveries don’t make a huge difference: they confirm, rather than contradict our understanding of evolutionary history. This is especially true of the fossil record of human origins from their monkey relatives, the investigators found. Though early human fossils are very rare, and new discoveries make a big splash in the scientific literature and in the media, they sit randomly across the evolutionary tree of early humans. In other words, the researchers said, most discoveries of new fossil species simply fill in gaps in the fossil record that we already knew existed. “Human fossils are very rare, and they are costly to recover because of the time involved and their often remote locations. Scientists may be pushed by their sponsors, or by news reporters, to exaggerate the importance of their new find and make claims that ‘this new species completely changes our understanding,’“ said James Tarver, leader of the study. The story of dinosaur evolution is a bit more complicated, he added. New dinosaur fossils are being found in places around the world where they’ve never been looked for before, such as China, South America and Australia. These fossils, the scientists said, are fundamentally challenging existing ideas about dinosaur evolution. But this seems to tell us that there are still many new species of dinosaurs out there in the rocks. “These are important results,” said Michael Benton, another member of the team. “It might seem negative to say that new finds do, or do not, change our views. However, to find that they don’t means that we may be close to saturation in some areas, meaning we know enough of the fossil record in some cases to have a pretty good understanding of that part of the evolutionary tree.” “We can use these studies as a way of targeting new expeditions,” added co-author Phil Donoghue. “If dinosaurs are poorly understood from a particular part of the world, or if some other group is altogether incompletely known, that’s where we need to devote greater efforts.”