Well i think what Acton is saying is interesting
If you draw a continous pedigree, he is infact correct, if we take out the option of inbreeding, 32 generations ago we shoudl techinically have 4.3 billion parents who would have contributed genes towards us. Obviously this isn't the case, so its interesting to note where intermingling would occur? So without any inbreeding whatsoever, assuming a 30 year generation gap, 32 generations would take us to about 1000 years back with 4.3 billion parents.
Another interesting note is that the entire aboriginese population was most probably derived from about 50 to 100 people who took rafts from southasia or africa to get to australia.
We all originated from a common ancestor, but interesting to note that our cells contain mitochondria which also has it's own dna.
Mitochondrial DNA doesn't go through recombination (correct me if im wrong here) and is carried over from the mother so it's interesting to note how much it has changed over time.
The haplogroups for Mtdna can identify different groups of people and map out human migration
see the list of haplo groups here:
Also interesting is the Y chromosome, which can also attempt to map out human migration:
quote from wikipedia:
The human Y chromosome has lost 1,393 of its 1,438 original genes over the course of its existence. With a rate of genetic loss of 4.6 genes per million years, the Y chromosome may potentially lose complete function within the next 10 million years. Comparative genomic analysis, however, reveals that many mammalian species are experiencing a similar loss of function in their heterozygous sex chromosome. Degeneration may simply be the fate of all nonrecombining sex chromosomes due to three common evolutionary forces: high mutation rate, inefficient selection and genetic drift. On the other hand, recent comparisons of the human and chimpanzee Y chromosomes show that the human Y chromosome has not lost any genes since the divergence of humans and chimpanzees between 6–7 million years ago, and only one gene since humans diverged from the rhesus macaque 25 million years ago, providing direct evidence that the linear extrapolation model is flawed.