Number of Ancestors

2^(elapsed time in years / 25)

Of course, this is assuming none if your ancestors had children with each other.

>>2710925
Isn't that a bit low of an estimate?

Hasn't someone done this already, while having taken into account the average lifespan and fertility throughout the ages?

>>2710909

Impossible to estimate due to inbreeding.

>>2712489
And assuming there's no inbreeding?

>>2712492

Then it doubles every generation (~20 years).

>tfw we are all inbred

>>2712492
Its properly called pedigree collapse. Ancestors will frequently repeat themselves in family trees because people will tend to mate with others in a similar geographic area and there will be some degree of genetic overlap in a stable population because it shares the same founders.

>>2713717
>pedigree collapse
Intredasting.

>Demographer Kenneth Wachtel estimates that the typical English child born in 1947 would have had around 60,000 theoretical ancestors at the time of the discovery of America. Of this number, 95 percent would have been different individuals and 5 percent duplicates. (Sounds like Invasion of the Body Snatchers, but you know what I mean.) Twenty generations back the kid would have 600,000 ancestors, one-third of which would be duplicates. At the time of the Black Death, he'd have had 3.5 million — 30 percent real, 70 percent duplicates. The maximum number of "real" ancestors occurs around 1200 AD — 2 million, some 80 percent of the population of England.
http://www.straightdope.com/columns/read/412/2-4-8-16-how-can-you-always-have-more-ancestors-as-you-go-back-in-time
(funny article, IMHO)

With that high numbers of ancestors, isn't it basically impossible for people not to be related? I always see people making genetic arguments about people that immigrated from geographically farther away to prove that they don't share any blood, but even assuming that breeding tends to happen only in walking distance, all it takes is for a single individual of your millions of ancestors to go a bit further away and procreate there.
Or not even that, because the genetic material could slowly crawl near in waves: For example, assume the 16th century Turkish villager in Anatolia procreating only in a walking distance. Let's say, 40km. In only 9 generations, he has already spread from Ankara to Constantinople (360km), if we take this lowest estimate. In only 20 generations, he's at the coast of Albania, provided he's a dumbass going over land only (800km). In another 19 generations, he's in Vienna (760km).

Also, the further you go back in the ancestry tree, the more guaranteed it is that an ancestor goes a much further distance. For example, the Roman from Latium may take a ship from Ostia to Syria. The Syrian trader may settle down in Massalia (Marseille). The migrating tribe migrates huge distances by default.

>>2713800
Eurasian Adam existed only 70,000 years ago. All non African male lineages descend from him.

>>2713800
Also, think about the role of war in genetics. War makes armies travel large distances. Pre-modern armies included a huge host of women and children, too. War led to the gain of slaves, with whom or their free offspring some people procreated eventually.
Also, war creates mercenaries that may settle down much farther away.