>How long is the growth cycle? six months? 2 years? 5 years? for a full
>adult body?
This strikes me as a misconception (so to speak), although an extremely
pervasive one. On the face of it, the growth cycle for a perfect 16 year
old young adult human body is 16 years. And it's hard to see how that can
be achieved without all the sensorimotor interactions a conscious person
has with the rich physical world, and with other people. The comic book
picture of healthy and muscular bodies growing suspended in fluid, ready
for cropping and transplantation, is entirely unhooked from everything we
know about mammalian developmental processes.
On the other hand, the real kicker in the headless frog embryo story is the
informed suggestion that we are nearing the point where functioning organs
can be cultured without requiring a whole body-brain complex to support
them. I don't see why this should be done drastically faster in vitro than
a body does it in vivo, but maybe there are ways to tweak the cycle if a
complete body isn't needed. Other mammals grow big and strong far faster
than we do, so maybe the latency plateau can be bypassed in decorticate
preparations.
Damien Broderick