Hi ya gerry & all silk here. I thought some of you might find this of interest. Check this:

"What­ever the imp­li­ca­tions of the recent findings, McKee added, they high­light a ubiq­ui­tous point about ev­o­lu­tion: “every spe­cies is a tran­si­tion­al spe­cies.”

This might mean that humans as we now know them one day will not exist.. we will have out evolved our selves so to speak.. wouldn't suprise me!

Human evolution, radically reappraised

Hu­man ev­o­lu­tion has been speed­ing up tre­mend­ous­ly, a new study con­tends—so much, that the lat­est ev­o­lu­tion­ary changes seem to large­ly ec­lipse ear­l­ier ones that ac­com­pa­nied mod­ern man’s “ori­gin.”

The stu­dy, along­side oth­er recent re­search on which it builds, amounts to a sweep­ing re­ap­prais­al of tra­di­tion­al views, which tended to as­sume that hu­mans have reached an ev­o­lu­tion­ary end­point.

The find­ings sug­gest that not on­ly is our ev­o­lu­tion con­tin­u­ing: in a sense our very “orig­in” can be seen as on­go­ing, a ge­net­i­cist not in­volved in the study said.

Greg­o­ry Coch­ran of the Uni­ver­si­ty of Utah in Salt Lake City, Utah, a co-author of the stu­dy, said the re­search may force a rad­i­cal re­think­ing of the sto­ry of mod­ern hu­man ev­o­lu­tion. “It turns it up­side-down, pret­ty much,” he said. But skep­tics ques­tion some as­pects of the work.

The tra­di­tion­al pic­ture of hu­mans as a fi­n­ished prod­uct be­gan to erode in re­cent years, sci­en­t­ists said, with a crop of stud­ies sug­gesting our ev­o­lu­tion in­deed goes on. But the new­est in­vest­i­ga­tion goes fur­ther. It claims the pro­cess has ac­tu­al­ly ac­cel­er­at­ed.

It al­so down­plays the im­por­tance of a much-scru­ti­nized era around 200,000 years ago, when hu­mans con­sid­ered “ana­tom­i­cally mod­ern” first ap­pear in the fos­sil rec­ord. In the stu­dy, this ep­och e­merges as just part of a vast arc of ac­cel­e­rat­ing change. 

“The or­i­gin of mod­ern hu­mans was a mi­nor event com­pared to more re­cent ev­o­lu­tion­ary chang­es,” wrote the au­thors of the re­search, in a pre­sent­a­tion slated for Fri­day in Phi­l­a­del­phia at the an­nu­al meet­ing of the Amer­i­can As­so­ci­a­tion of Phys­i­cal An­th­ro­po­l­o­g­ists.

The au­thors are Coch­ran and an­thro­po­l­o­gist John Hawks of the Uni­ver­si­ty of Wis­con­sin-Ma­d­i­son. The find­ings will also be sub­mitted to one or more sci­en­t­i­f­ic jour­nals, Coch­ran said. 

The pro­pos­al is “truly fas­ci­nat­ing,” wrote Uni­ver­si­ty of Chica­go ge­net­i­cist Bruce Lahn in an e­mail. He was­n’t in­volved in the work, though he did con­duct ear­li­er re­search find­ing that ev­o­lu­tion may still be on­go­ing in the brain.

Even be­fore the Hawks-Cochran study and its im­me­di­ate fore­run­ners, Lahn wrote, sci­en­tists had al­ready not­ed a trend of ac­ce­le­rating change in the ev­o­lu­tion­ary line­age lead­ing to mod­ern hu­mans from ape-like an­ces­tors. But that phe­nom­e­non seemed to have oc­curred over time spans meas­ured in mil­lions of years; it was far from clear that it has con­tin­ued in the re­cent past or to­day, he added.

Hawks and Cochran, by con­t­rast, ar­gue that the trend “is vis­i­ble even in the last tens of thou­sands of years,” Lahn wrote. It “runs count­er to the feel­ing in some quar­ters that the ev­o­lu­tion of the hu­man phe­no­type [form] has slowed down or even stopped in our re­cent past.”

Defining an origin

If the study is cor­rect, it raises new ques­tions about how to de­fine the “orig­in” of mod­ern hu­mans—a rath­er ar­bi­trary de­ci­sion in any case, Lahn re­marked.

The or­i­gin is “de­fined prob­a­bly more as a mat­ter of con­ven­ience rath­er than re­flect­ing any ac­tu­al wa­ter­shed ev­o­lu­tion­ary event,” he wrote. That is, it’s “use­ful to say that any past crea­tures that are with­in cer­tain lev­els of sim­i­lar­i­ties to us to­day should be con­sid­ered as ‘the same’ as us.”

But if the changes that ac­com­pa­nied this event are on­ly a tri­fling part of a wid­er trend, he added, it be­comes rea­son­a­ble to ask wheth­er that fur­ther de­flates the ra­tion­ale for call­ing it an or­i­gin.

“In a sense,” he wrote, one could say “the or­i­gin is still on­go­ing.”

Ev­o­lu­tion oc­curs when an in­di­vid­ual ac­quires a ben­e­fi­cial ge­net­ic mu­ta­tion, and it spreads through­out the pop­u­la­tion be­cause those with it thrive and re­pro­duce more. Cease­less repe­ti­tions of this can change spe­cies, or pro­duce new ones. As ben­e­fi­cial genes spread, harm­ful ones are weeded out; the whole pro­cess, called nat­u­ral se­lec­tion, pro­pels ev­o­lu­tion.

Hawks and Cochran an­a­lyzed mea­sure­ments of skulls from Eu­rope, Jor­dan, Nu­bia, South Af­ri­ca, and Chi­na in the past 10,000 years, a pe­ri­od known as the Hol­o­cene era. They al­so stud­ied Eu­ro­pean and West Asian skulls from the end of the Pleis­to­cene era, which lasted from two mil­lion years ago un­til the Hol­o­cene.

“A con­stel­la­tion of fea­tures” changed across the board, Hawks and Cochran wrote in their pres­en­ta­tion. “Hol­o­cene changes were si­m­i­lar in pat­tern and... faster than those at the archaic-mod­ern tran­si­tion,” the time when so-called mod­ern hu­mans ap­peared. But these changes “them­selves were rap­id com­pared to ear­li­er hom­i­nid ev­o­lu­tion.” Ho­mi­n­ids are a fam­i­ly of pri­mates that in­cludes hu­mans and their ex­tinct, more ape-like though up­right-walk­ing an­ces­tors and rel­a­tives.

Hawks and Cochran al­so ana­lyzed past ge­net­ic stud­ies to es­ti­mate the rate of prod­uction of genes that un­der­go pos­i­tive se­lec­tion—that is, genes that spread be­cause they are ben­e­fi­cial. “The rate of gene­ration of pos­i­tively se­lected genes has in­creased as much as a hun­dred­fold dur­ing the past 40,000 years,” they wrote.

There are ways to de­tect po­si­tive se­lec­tion in ge­nome data. But Mark Thom­as, a ge­net­ic an­thro­pol­o­gist at Uni­ver­si­ty Col­lege Lon­don, was skep­ti­cal that these would be enough to make Hawks’ and Cochran’s case. “The is­sue is that the most pow­er­ful meth­ods for de­tect­ing se­lec­tion are ones that lose their sen­si­tiv­i­ty go­ing more than 30,000 years back,” he said. Oth­er tech­niques can’t “dis­tin­guish be­tween se­lec­tion and pop­u­la­tion growth.”

Thom­as added that he under­stands the ske­le­tal data to show some­thing dif­ferent from what Hawks and Coch­ran say, but that he would need a ful­ler ac­count of their find­ings to make a judg­ment.

Worrisome findings?

Hawks and Coch­ran said some of the most no­ta­ble phys­i­cal changes in hu­mans have been ones af­fect­ing the size of the brain case.

A “thing that should prob­a­bly wor­ry peo­ple is that brains have been get­ting smaller for 20,000 to 30,000 years,” said Coch­ran. But brain size and in­tel­li­gence aren’t tightly linked, he added. Also, growth in more ad­vanced brain ar­eas might have made up for the shrinkage, Coch­ran said; he spec­u­lated that an al­most break­neck ev­o­lu­tion of high­er fore­heads in some peo­ples may re­flect this. A study in the Jan. 14 Brit­ish Den­tal Jour­nal found such a trend vis­i­ble in Eng­land in just the past mil­len­ni­um, he noted, a mere eye­blink in ev­o­lu­tionary time.

Research pub­lished in the Sept. 9, 2005 is­sue of the re­search jour­nal Sci­ence by Lahn and col­leagues found that two genes linked to brain size are rap­idly evolv­ing in hu­mans.

An­thro­po­l­o­gist Jef­frey Mc­Kee of Ohio State Uni­ver­si­ty said the new find­ings of ac­ce­l­er­ated evolution bear out pre­dic­tions he made in a 2000 book The Rid­dled Chain. Based on com­put­er mod­els, he ar­gued that ev­o­lu­tion should speed up as a pop­u­la­tion grows. This is be­cause pop­u­la­tion growth cre­ates more op­por­tu­ni­ties for new mu­ta­tions; al­so, the ex­pand­ed pop­u­la­tion oc­cu­pies new en­vi­ron­men­tal niches, which would drive ev­o­lu­tion in new di­rec­tions.

Lahn said he’s not con­vinced that the ac­cel­er­at­ed phys­i­cal ev­o­lu­tion is tied to pop­u­la­tion growth. “It may be a long way be­fore” an­yone can test the truth of this, he wrote.

But oth­er fac­tors could al­so ex­plain an accele­ration, ac­cord­ing to an­thro­po­l­o­gist John Kings­ton of Em­o­ry Uni­ver­si­ty in At­lan­ta, Ga. Ev­o­lu­tion might speed up be­cause we have changed our own en­vi­ronment, which in turn changes the ev­o­lu­tion­ary pres­sures. “We now con­trol our own en­vi­ronment and ecol­o­gy to some ex­tent,” he said.

For instance, if you in­vent spears, you per­haps can af­ford to be slight­er-framed be­cause you can stand fur­ther away from wild an­i­mals, Coch­ran said. He ar­gued that a pow­er­ful syn­er­gy be­tween these sorts of changes and expand­ing pop­u­la­tion ex­plains the “fant­as­tic­ally ra­pid” re­cent evo­lu­tion.

“A very big change”

Ove­rall, the find­ings could amount to “a very big change” in tra­di­tion­al think­ing for two rea­sons, ac­cord­ing to Mc­Kee. First, he said, many re­search­ers had mis­tak­en­ly as­sumed pop­u­la­tion growth would slow down ev­o­lu­tion, be­cause new mu­ta­tions would take too long to spread through a large pop­u­la­tion. 

Sec­ond, the find­ings deal a fi­nal blow to a lin­ger­ing view among re­search­ers of ev­o­lu­tion as a pro­cess “with us as the be-all-end-all,” he said. That idea went out of fash­ion in the 1950s but still per­sists “in the backs of our minds,” he added.

Many of the changes found in the ge­nome or fos­sil rec­ord re­flect me­tab­o­lic alt­er­a­tions to ad­just to ag­ri­cul­tur­al life, Cochran said. Oth­er changes simp­ly make us weaker.

In the June 2003 is­sue of the re­search jour­nal Cur­rent An­thro­po­l­ogy, Hel­en Leach of the Uni­ver­si­ty of Ota­go, New Zea­land wrote that skele­tons from some pop­u­la­tions in the hu­man line­age have un­der­gone a pro­gres­sive shrink­age and weak­en­ing, and re­duc­tion in tooth size, si­m­i­lar to changes seen in do­mes­ti­cat­ed an­i­mals. Hu­mans seem to have do­mes­ti­cat­ed them­selves, she ar­gued, caus­ing phys­i­cal as well as men­tal changes.

De­spite all the alte­rations, Mc­Kee said he be­lieves the no­tion of an “o­rig­in” of mod­ern hu­mans around 200,000 years ago re­mains use­ful. “It’s just a thresh­old point” at which hu­mans take on most of the phys­i­cal fea­tures we rec­og­nize, he re­marked, and as such, need­n’t be dis­carded. Coch­ran said it can still be ar­gued that the key change was lang­uage; but when this ori­gi­nated re­mains far from clear. 

What­ever the imp­li­ca­tions of the recent findings, McKee added, they high­light a ubiq­ui­tous point about ev­o­lu­tion: “every spe­cies is a tran­si­tion­al spe­cies.”                                        

                                                           chao/Silk