Evolutionary Changes?

Hard sf writers scientifically rationalise FTL, time travel, immortality, telepathy, teleportation etc. James Blish's They Shall Have Stars is an extended rationale for antia-gathics and antigravity, the twin premises of his Cities In Flight Tetralogy. This blog recently listed three of Poul Anderson's rationalisations for FTL and his one explanation of instantaneous space jumps.

Let us consider immortality. Blish's anti-agathics are a range of drugs that counteract the various aspects of the aging process. Heinlein's Howard Families breed for longevity. Others, wanting to emulate the Howards, find a way to prolong life by renewing blood. In one of Larry Niven's futures, the chemicals associated with aging can be teleported out of the body. That is neat.

(This is one exercise in imagination: combine two basic sf premises and see what results. In this case, the instant elsewhere is a young forever. Another example, in Anderson's There Will Be Time, is the equation: STL + time travel = FTL.)

In Anderson's World Without Stars (New York, 1966), the antithanatic is a synthetic virus that destroys any cells "...that do not quite conform to the host's genetic code." (p. 20)

I agree with correspondent Sean's comment that this would tend to prevent evolutionary changes in humanity - but there are other factors. In the orbiting starport, City, Argens' portwife, Lute "...lives in high-weight, overlooking space itself. That's expensive..." (p. 9) Thus, physically, other port dwellers must live permanently in lower weight. That will affect their body size and shape.

Mentally, regular contact with other races must change perspectives. There are "...the usual linguistic problems..." which are greater than usual with the intergalactics because " '...they came from such an alien environment.'" (p. 21) Nevertheless, conversation is established so a multi-species worldview will eventually emerge.

Indefinitely prolonged life-spans, although they prevent physical mutations, must also affect perspectives.

"One thing that we have all gained in our centuries is patience." (p. 16)

Memories must be regularly edited and this would change perspectives even more. How much sense of identity would a man retain with his earlier life? How will he regard current experiences when he knows that, years or decades hence, he will edit most of his memories although he himself, barring accidents, will continue to live for centuries and millennia? Death will not come from old age but can come unexpectedly at any time. Instead of working, saving and retiring, an individual will work, save, spend time between jobs, then work again, indefinitely. Fortunately, there is a universe to explore although a few prefer "...timeless oneness with the planet." (p. 8) These sound like major psychological and social changes to mankind.