the chicken or the egg …

Dinosaurs before birds. Re-engineering with alligator DNA, is that birds with a bite?:

Scientists re-engineer bird beak to ancestral “dino” state
Research aimed to retrace some of the evolutionary steps that gradually transformed dinosaurs into birds.

An artist’s rendition of the nonavian dinosaur Anchiornis and a modern bird, a tinamou. (Courtesy John Conway & Yale U.)

The re­search team, led by Yale Uni­vers­ity pa­le­on­tol­ogist and de­vel­op­mental bi­ol­o­gist Bhart-Anjan S. Bhul­lar and Har­vard Uni­vers­ity de­vel­op­mental bi­ol­o­gist Ar­hat Abzhanov, used the fos­sil rec­ord as a guide. The sci­en­tists said they trans­formed chick­en em­bryos in­to spec­i­mens with a snout and pal­ate some­what like that of small di­no­saurs such as Ve­loci­rap­tor and Ar­chae­op­ter­yx.

The goal “was to un­der­stand the mo­lec­u­lar un­der­pin­nings of an im­por­tant ev­o­lu­tion­ary tran­si­tion,” said Bhullar, lead au­thor of the stu­dy, pub­lished on­line May 12 in the jour­nal Ev­o­lu­tion. “Lit­tle work has been done on what ex­actly a beak is, an­a­tom­ic­ally, and how it got that way.”

The sci­en­tists first an­a­lyzed the anat­o­my of re­lat­ed fos­sils and liv­ing an­i­mals to out­line how the tran­si­tion might have oc­curred. Next, they searched for pos­si­ble shifts in gene ac­ti­vity, or gene “ex­pres­sion,” cor­re­lat­ing with the tran­si­tion. Fi­nally they used chem­i­cals known as small-molecule in­hibitors to block the ac­ti­vity of pre­sumed beak-spe­cif­ic genes.

This not only caused the beak to re­vert to an an­ces­tral state—it had a si­m­i­lar ef­fect on a bone at the roof of the mouth called the pal­a­tine bone, they said. This shows that “a sin­gle, sim­ple de­vel­op­mental mech­an­ism can have wide-rang­ing and un­ex­pected ef­fects,” Bhullar said.

The work took Bhullar from the al­li­ga­tor nests at Rock­e­fel­ler Wild­life Ref­uge in south­ern Lou­i­si­ana to an emu farm in Mas­sa­chu­setts. He ex­tracted DNA from var­i­ous spe­cies in or­der to clone frag­ments of ge­net­ic ma­te­ri­al to look for spe­cif­ic gene ex­pres­sion.

The re­search has sev­er­al im­plica­t­ions, Bhullar said. For ex­am­ple, if one mo­lec­u­lar mech­an­ism caused the trans­forma­t­ion, there should be a cor­re­spond­ing change in the fos­sil rec­ord. The rec­ord bears that out so far, he ar­gued. For ex­am­ple, an an­cient rel­a­tive of mod­ern birds known as Hes­per­o­nis has both the mod­ernized pal­a­tine bone and the mod­ernized beak. The lat­ter is vis­i­ble in the so-called pre­max­il­lae—bones at the tip of the up­per jaw, which in birds are en­larged and fused to form the beak.

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About Tom Harley

Amateur ecologist and horticulturalist and CEO of Kimberley Environmental Horticulture Inc. (Tom Harley)
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