>I suppose this means second gen Detians like Kate could regress all
>the way back to at least a fetal state, possibly farther, but one

No. Second-generation Detians aren't really Detians until they reach adulthood, barring special circumstances. They grow and age normally, and except for a slightly accelerated healing rate and greater resistance to disease, are more or less normal in every other respect too. (That's why Kate's slightly nearsighted.) They don't regenerate, and they can't control their aging rate.

When they've completed their growth cycle (which varies from individual to individual, but tends to be around age twenty), they undergo aging freeze, gaining the full regenerative abilities in the process. Basically, they hit young adulthood and stop, unless they decide to keep going. If they do, they can age back to where they froze, but no farther back.

Circumstances can force the Detian genome's hand before the time is right; if a Detian child suffers a life-threatening injury (or disease, but these are much, much rarer) before adulthood, there's a chance she'll undergo premature freeze, fixing her age baseline at whatever her current age is, so that her regenerative powers will kick in and save her life. The younger the child, the less likely it is that this will work.

This survival effect can have very unfortunate consequences: in some cases, a regenerative disease called Edgerton's Syndrome results. This manifests itself as an inability to permit further aging. The victim is trapped at whatever age she was at when she suffered the injury. This is clearly less than optimal in most cases, and explains why, though it's possible for a properly trained and equipped medical facility to induce premature freeze, they are very reluctant to do so under all but the most extreme conditions.

--G.
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Benjamin D. Hutchins, Co-Founder, Editor in Chief, Netadmin
Eyrie Productions, Unlimited http://www.eyrie-productions.com/