Aren’t epi­ge­netic ef­fects ev­i­dence for La­mar­ck­ism?

Focus-Science and Technology - - Q&A - SALLY EL­LIS, LV

NOT REALLY. EPI­GE­NET­ICS is

when genes al­ter their ac­tiv­ity in re­sponse

to ex­ter­nal fac­tors such as diet, ex­er­cise

and chem­i­cal ex­po­sure. The se­quence of

let­ters in the DNA doesn’t change, but the

DNA mol­e­cule ac­quires other chem­i­cal

changes that can be passed on to your

off­spring. Th­ese in­her­ited traits last for

two or three gen­er­a­tions.

La­mar­ck­ism says the gi­raffe got its long

neck be­cause par­ents stretched their own

necks slightly dur­ing their life­times and

passed that in­crease on to their chil­dren,

and so on. That’s quite dif­fer­ent from the

Dar­winian view that each gen­er­a­tion has

a cer­tain amount of nat­u­ral vari­a­tion, and

that gi­raffes with longer necks have more

off­spring. Epi­ge­net­ics is an im­por­tant

in­flu­ence on evo­lu­tion, but it doesn’t

drive long-term species change.

Gi­raffes’ necks are an evo­lu­tion­ary puz­zle

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