What is the minimum number of humans possible...

[Bill Morris]

From TNG: Up the Long Ladder

PULASKI: Thirty couples are enough to create a viable genetic base. But the broader the base the safer and healthier the society. It would be best if each woman--Mariposan and Bringloidi-had at least three children by three different men.

 

[darkwing_duck1]

That's way off-topic, but...

Spoiler: BSG

Ellen was the last of the Five; her original died 2000 years ago. But Kara seems to have been newly downloaded at the end of last season -- there were twelve known models, and she's a new addition, a thirteenth. At least, that's how I see it.

This would make sense given the speculation awhile back that

Spoiler: BSG

the humans of this cycle are all descendents of the organic Cylons of the previous one. Kara being the 13th Cylon would parallel the 13 tribes of Kobol....

 

[USS Triumphant]

Spoiler: BSG

the humans of this cycle are all descendents of the organic Cylons of the previous one. Kara being the 13th Cylon would parallel the 13 tribes of Kobol....

And that might mean:

Spoiler: BSG

that, like that scene in the Cylon basestar with all the Sharons, the 13th tribe might be entirely made up of Karas. When they get to the real Earth, there will be Starbucks on every corner!

 

[SicOne]

Geez, Triumphant, you're killin' me here...

 

[SicOne]

You guys do make sense, though, with the show revealing Ellen as the 12th, but still needing an explanation about Kara Thrace and the body she found in the wrecked viper...her as the 13th, analogous to the 13th tribe, does make sense.

 

[ancient]

Back on topic, simple math means that if you want the max number of combos with the least people, you need exactly the same number of men and women. This allows for the max number of couples.

For example, if you have only 6 people:

0 men / 6 women: ZERO possible combinations.
1 men / 5 women: FIVE possible combinations.
2 men / 4 women: EIGHT possible combinations.
3 men / 3 women: NINE possible combinations.
4 men / 2 women: EIGHT possible combinations.
5 men / 1 women: FIVE possible combinations.
6 men / 0 women: ZERO possible combinations.

 

[Albertus]

Its been a while, but the last Global Extinction Event is due. 10K people was the last amount I heard that kept the Human race alive, But maybe half that, 5000 could keep the light shining.

I guess its down to: who will you mate with?

 

[FalTorPan]

Back on topic, simple math means that if you want the max number of combos with the least people, you need exactly the same number of men and women. This allows for the max number of couples.

For example, if you have only 6 people:

0 men / 6 women: ZERO possible combinations.
1 men / 5 women: FIVE possible combinations.
2 men / 4 women: EIGHT possible combinations.
3 men / 3 women: NINE possible combinations.
4 men / 2 women: EIGHT possible combinations.
5 men / 1 women: FIVE possible combinations.
6 men / 0 women: ZERO possible combinations.

It isn't quite that simple, since multiple children from any single pair of parents don't have identical DNA.

 

[ancient]

Back on topic, simple math means that if you want the max number of combos with the least people, you need exactly the same number of men and women. This allows for the max number of couples.

For example, if you have only 6 people:

0 men / 6 women: ZERO possible combinations.
1 men / 5 women: FIVE possible combinations.
2 men / 4 women: EIGHT possible combinations.
3 men / 3 women: NINE possible combinations.
4 men / 2 women: EIGHT possible combinations.
5 men / 1 women: FIVE possible combinations.
6 men / 0 women: ZERO possible combinations.

It isn't quite that simple, since multiple children from any single pair of parents don't have identical DNA.

Well yeah, each person should also have at least one male and female child, but the more the merrier. So having nine couples having kids is the best situation.

If there are exactly even numbers of M/F, it's pretty easy to figure out how many people you need to start off with in order to get through however many generations with no one being forced to marry a cousin.

So, if you start with even numbers and each couple has at least one male & female child...

...Starting with 2 people: people in the 2nd generation have to mate with their sibling. Ouch.

...Starting with 4 people: people in the 3rd generation have to mate with their 1st cousin.

...Starting with 8 people: people in the 4th generation have to mate with their 2nd cousin.

...Starting with 16 people: people in the 5th generation have to mate with their 3rd cousin.

...Starting with 32 people: people in the 6th generation have to mate with their 4th cousin.

...Starting with 64 people: people in the 7th generation have to mate with their 5th cousin.

...Starting with 128 people: people in the 8th generation have to mate with their 6th cousin.

...Starting with 256 people: people in the 9th generation have to mate with their 7th cousin.

...and so on. This assumes every male mates with every female that is not related to him at all up until the generation that has no choice but to go for the cousin, and they each have at least 1M/1F for kids. How good this all works out heavily depends on the original generation. If you don't have exactly even numbers, the number of generations that can go without mating with a cousin goes way down. If you have 1 man and 255 women, the first generation has to mate with half-brothers/sisters.

 

[SicOne]

Thanks, guys, to everyone who participated in this topic...and for indulging my aside into Galactica.

By the way, missed the last few episodes...what's the count?

op

 

[Stardate]

I read in some black death historic book that it says we need a least 10,000 people to keep human race alive and healthy.

 

[Albertus]

I found the report below, but I remember it from a Horizon (science) programme in the UK:

"About 3000 generations ago – a mere blink of an eye in the evolutionary timescale – the human population of Earth dwindled to the point where everyone on the planet could have fitted inside a small football stadium. Mounting DNA evidence indicates that the human population was reduced to perhaps fewer than 10,000. One study even suggests that the number of women dropped to just 500 individuals. For centuries, each new generation of Homo sapiens could easily have been the last."

Full article:
http://www.readersdigest.com.au/content/printContent.do?contentId=90890

Although, I have seen numbers as low as 2,000 cited. It seem that diversity might depend, as has previously been observed in this thread, on the ratio of male to female. More male, less female sems the way we have gone.

Actually, Gene combinations (dominant/recessive) work like algebra: Two pluses make a plus, two minuses make plus, a plus and minus make a minus. So you can make your own calculations as to species survival at home!!!

Hope that helps.

 

[SicOne]

Interesting article, thanks, Albertus. There was also a Wikipedia article on the Toba eruption that was interesting, though as always with Wikipedia, trust but verify...

 

[Tiberius]

Approximately 50,000 years ago, cheetahs were reduced to about 7 breeding pairs. We can tell because of a greater assymetry in their faces (an indication of inbreeding), and the fact that skin grafts between non-related individuals take much more often than with other cat species.

If Trek and BSG both have genetically diverse populations of Humans stemming from a population of about 50,000 individuals, that is more than enough to prevent inbreeding.

But don't think of it as having enough geneteic diversity to avoid inbreeding. Think of as the larger the population, the less effect inbreeding has (because it you need more generations before two related people are likely to produce offspring, and in those generations, the genes from their sides of the family tree will have been diluted by genes from other non-related individuals). With a large enough population, the effect of inbreeding is reduced to the point of negligence.

Here's an example. We have two people, A and B. They have children, C and D. If C and D are to reproduce, they must mate with each other (assuming one male and one female). This leads to inbreeding.

However, if we start out with a larger population, we will have A and B as one pair, and 1 and 2 as another pair. A and B have offspring C and D as before, and 1 and 2 produce offspring 3 and 4.

So, C can produce children with 3, and D mates with 4. This avoids inbreeding for that generation. In the next generation, C3 and D4 will need to mate with relatives, but their genes are more different because of the fresh genetic material from 1, 2, 3 and 4. With a larger population, this effect gets stronger, and when two related people reproduce, they are not very closely related.

If I was to meet a woman who was a related to me (assuming I met her randomly and not at a family reunion), it would be likely that our most recent common relation was several generations ago, such as a great great great great great grandparent. Thus, any inbreeding effects would be minimal and wouldn't produce a signiicant risk.