Page 234 - The Evolution Impasse 2

All hu man be ings on Earth share bas i cal ly the same ge net ic in for ma tion, but thanks to
the var i a tion po ten tial per mit ted by this ge net ic in for ma tion, they of ten look very dif fer -
ent from one an oth er.

ing is al ways lim it ed, and that there fly re mains a fruit fly; a rose, a rose,
is a lim it to the var i a tions that any and so on. 269
one spe cies can un der go. Variations and their var i ous
Indeed, in the in tro duc tion to chan ges are re strict ed in side the
their book Natural Limits to Biological bounds of a spe cies' ge net ic in for ma -
Change Professor of Biology Lane P. tion, and they can nev er add new ge -
Lester and the mo lec u lar bi ol o gist net ic in for ma tion to spe cies. For that
Raymond G. Bohlin wrote: rea son, no var i a tion can be re gard ed
That pop u la tions of liv ing or gan isms as an ex am ple of ev o lu tion.
may change in their anat o my, phys i ol - The Danish sci en tist W. L.
o gy, ge net ic struc ture, etc., over a pe ri - Johannsen sum ma ri zes the sit u a tion:
od of time is be yond ques tion. What re -
The var i a tions up on which Darwin
mains elu sive is the an swer to the
and Wallace placed their em pha sis can -
ques tion, How much change is pos si -
not be se lect ive ly push ed be yond a cer -
ble, and by what ge net ic mech a nism
tain point, that such var i a bil i ty does
will these chan ges take place? Plant
not con tain the se cret of "in def i nite de -
and an i mal breed ers can mar shal an 270
par ture."
im press ive ar ray of ex am ples to dem -
The fact that there are dif fer ent
on strate the ex tent to which liv ing sys -
hu man ra ces in the world or the dif -
tems can be al tered. But when a breed -
fer en ces be tween par ents and chil -
er be gins with a dog, he ends up with a
dog—a rath er strange look ing one, dren can be ex plained in terms of
per haps, but a dog none the less. A fruit var i a tion. Yet there is no ques tion of
The Evolution Impasse II