Question for evolutionists

Imagine that we have a time machine by which we could bring forward to our time any
individual from the past. We could set our time machine to the period of the Roman
occupation and bring forward Queen Cleopatra. Assuming that she is a normal healthy
woman, she could marry a modern man and they would have children. We could then set
our time machine further back in time to bring forward a female say from the last
Ice Age. Again assuming that she is a normal healthy woman, she could marry a modern
day man and they would have children. We could repeat this procedure, going back
further and further in time and bring forward a female ancestor each capable of mating
with a modern man and producing children. At some point in tmie, the female who would
be brought forward could not produce children if she mated with a modern man.
The time machine could also be used to be forward male ancestors which then could mate
with a modern females and produce children. Again at some point in time, the male
who would be brought forward could not get a modern female pregnant. The diagram below
illustrates: where the letter "G" repesents a generation (male or female) who could
be brought forward, the period "." represents for right now an udefined time, and the
letter "C" represents the current time.

__Unable to Produce___Transition
_____Children_________Period_________Able to Produce Children__________Current
_!...............................!..........................!......................................................................!
_GG........................GGGG..................GGGG............................................................GGGC

Question 1:
How long is the Transition Period? With the "time machine", we could bring
forward one generation at a time (C-1,C-2,.....C-T,C-[T+1],...). Would there
be a generation "T" such that the individual brought forward could breed with
the opposite modern day sex, but an individual from the previous generation
[(T-1)] could not breed with the opposite modern day sex?
Question 2:
During the Transition Period, intermediate forms should be formed which we
could call a modification. When a modification occurs, how many individuals
intially have the modification and how does the modification spread though
the population? Also at what rate do the modifications occur?
Question 3:
Not that I recommend it, but is it theoretically possible for humans to be
breed with other primates (such as apes or chimpanzees)?

Aha! Something I can answer out of my lurid university past (yes, I really WAS a biology teacher at one time.)

Excellent questions, by the way.

Originally posted by jagdflieger
Question 1:
How long is the Transition Period? With the "time machine", we could bring
forward one generation at a time (C-1,C-2,.....C-T,C-[T+1],...). Would there
be a generation "T" such that the individual brought forward could breed with
the opposite modern day sex, but an individual from the previous generation
[(T-1)] could not breed with the opposite modern day sex?

Quite a good question! A definition to start things off here: Hybrids are the offspring of parents that differ in one or more genetic traits. Hybrid is a general term; where appropriate, it may be used to describe the offspring of parents either from the same or from different species. The mating of individuals from different strains, breeds, or species is known as crossbreeding.

And another definition that will help answer: Although hybrid vigor is a desirable trait, species hybrids also usually possess one significant undesirable characteristic--they tend to be sterile and thus cannot reproduce. Generally, the degree of sterility is related to how closely the parents are related: the less closely related, the less fertile their offspring.

Crossbreeding is GENERALLY successful between members of the same genus but different species. Lions and tigers can crossbreed, but are often sterile.

So, theoretically, the species of hominids closest to our timeline would still be able to breed with modern man. You could expect fertile offspring and a breeding colony with homo sapiens sapiens and homo sapiens neanderthalis.


Homo erectus (lived 1,800,000 - 250,000 years ago) anthro.palomar.edu... was close enough to us in size and shape and genetics to breed with homo sapiens.

So, from LEAST likely to most likely, the list goes:
Homo habilis
Homo georgicus
Homo erectus
Homo ergaster
Homo antecessor
Homo heidelbergensis
Homo sapiens neanderthalensis
Homo sapiens sapiens

(definitions about them can be found here:
www.talkorigins.org...

So, any species of homo whateveritis from about 2.4 million years ago could theoretically breed with modern homo sapiens. You'd expect the habilus-sapiens cross to be mostly sterile, and the least number of sterile children in the homo sapiens sapiens-homo sapiens neanderthalis crosses.

Question 2:
During the Transition Period, intermediate forms should be formed which we
could call a modification. When a modification occurs, how many individuals
intially have the modification and how does the modification spread though
the population? Also at what rate do the modifications occur?

Basically, the transitions are so slight that you have trouble answering this. It's like having someone with a Black ancestor -- at what point do they look so Caucasian that you can't tell there's any African or Aborigine in their makeup?

Spreading thorugh the population depends on how fast they interbreed (they may attract NO mates, for example) and what the cultural practices are ("political marriages" (for land or water/hunting rights or political gain) were one practice that spread the genes more quickly ("I don't care HOW ugly she is, you're going to marry her and have babies with her!!")

And "modification" is hard to measure. Is it "brown eyes" or "curly hair" or what?

Question 3:
Not that I recommend it, but is it theoretically possible for humans to be
breed with other primates (such as apes or chimpanzees)?

Excellent question, and one that's been speculated about before. You'd have better luck trying the australopithecines (which are closely related to us). But in either case, the answer should be "no."

Chimpanzees are Pan troglodytes; not a human species (homo). Best luck you would have is with an ancestral chimpanzee and one of the oldest australiopithecenes... but that'd be awfully iffy.

[Edited on 2-6-2003 by Byrd]

...and to answer a possible next question, chimpanzee/ape lineage diverged from human lineage long before australopithecenes -- best fossil evidence is that it occurred somewhere about 5 to 7 million years ago:
www.n2.net...


[Edited on 2-6-2003 by Byrd]