Monday, July 9, 2018

Guest post with author Susan Kelley - Minimal Viable Population

I'm still enjoying some family vacation time, but I have a special treat for you. Please welcome the wonderful Susan Kelley to my blog!


MVP: Minimal Viable Population
I’m thrilled to be here on Christine’s blog and take it over for a day. Let’s talk some genetics science stuff.
Survivors of the Apocalypse, my three book dystopian romance series, is set three hundred years in the future. A virus has nearly wiped out mankind. Inside a doomed city are thousands of people, surviving by keeping their sterile city completely closed to the outside. But there are people outside the doom who survived the pandemic. They’re living rugged, frontier lives, but they have plenty of resources. The thing they don’t have is a large population.

This forces the frontiersman to reach out to the city, hoping to recruit people so they can maintain a MVP, minimal viable population. What is that number for humans? There are many examples in science of species being brought back from extinction, some with as few as one breeding couple. But what about humans?

There are plenty of opinions on that, ranging from 50 couples to 10,000 or even 50,000. The TV show Salvation put that number at 160, which is a number sometimes quoted in the scientific community. The population would have to careful to prevent inbreeding. Why is inbreeding bad? After all, many of the old noble houses in Europe, and let’s not forget the Tsars of Russian, who married relatives for generations. And that most famous of fictional inbreeding stories, Game of Thrones, showcases how common though not always accepted marrying a close relative was in medieval times. Here’s an interesting debate on those numbers.

Now for the bad:

Any birth defects that are in the family line become more likely to appear.
Genetic issues that are recessive are more likely to come up if related people have offspring.
Successive generations of close inbreeding will decrease the diversity more and increase the rate of bad mutations.

Siblings or parents and kids (super disgusting) marrying are the worst. They share 50% of their DNA. First cousins share 12.5% and until rather recently, wasn’t considered that bad of a thing. Before people became more mobile, most people were born, lived, and died within less than a ten-mile radius. They didn’t have many options. It was also a way to keep wealth within the family. Once people moved around more and women had more say in their futures, first cousin marriage started to be frowned upon. In some parts of the USA, it is against the law though the US is the only western country that has such a prohibition. However, there are groups of people in the world who still practice it. Read more interesting facts about cousins marrying.

On the fictional series like Game of Thrones, we see the Targaryens have many family members who suffer from some mental issues. But what we really want to know is if Jon and Daenerys should have children, being aunt and nephew? Most of today’s societies would consider that an incestual relationship. But then again, it’s in Westeros.

But back to my series, the outsiders are smart enough to understand they need a larger gene pool. But can the city people survive the outside air where the virus still lurks? Can the outsider people possibly convince the city folks that a match with a rugged frontiersman is the best thing for mankind?



The last book in the series, Exile’s Savage Lady, is now available along with the first two books at all major eBook retailers. Robin Linden was saved was saved by the outsiders when he was exiled from the city by a corrupt government. Now he’s determined to return to the city and bring the cure to the starving, oppressed population. Kerry Gibbs was raised with her brothers on the wild frontier and isn’t afraid of anything. Until he realizes she might lose the strong, quiet big man back to the city he feels responsible for saving. Her only choice is to sneak into the city with Robin and make sure he doesn’t get himself killed. Robin is willing to sacrifice himself to save those unfortunates, but Kerry is going to do everything she can to make sure he survives. The city is a dangerous place and neither of them may make it out alive.


Susan Kelley has been writing for more than ten years and has nineteen published romances. She resides in a large country home in central Pennsylvania where she has raised six children alongside her husband of many years. Deer, turkeys, hawks, and other wildlife cavort outside the window of her office where she writes fulltime. Find her:


What do you think about marrying cousins? How close is too close? How many people would you put on a ship to populate a space colony?

31 comments:

  1. Cousins are too close. With the population today and the amount of potential defects, it would take a good chunk to keep humans going safely. (Since we don't have the luxury of beginning with two perfect humans like God did with Adam and Eve.)

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    1. The cousins thing is creepy and a little too close to GoT, but my research shows it was very common in the past.

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  2. I immediately thought of Salvation's 160 as I was reading :)
    There was a Star Trek TNG episode that was about this as well - combining 2 societies (one was clones I think) and how many children women should have by how many different men.

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    1. Really sounds like some cold planning, doesn't it. I would think the careful matching would have to go on for generations.

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  3. Congrats on your book, Susan. It raises some interesting issues that we may deal with as people have fewer kids. Also it's an issue in some countries of not enough girls. Breeding too closely in families isn't the answer.

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    1. Science fiction could become our reality quicker than we expect. There are still countries that do a lot of cousin marrying.

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  4. Such an interesting topic! I don't have any cousins, so I've never given the issue much thought in terms of first cousins marrying. I can see how it could be a risky thing in terms of having kids, yet it's commonly practiced in so many places.

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    1. It's not even an issue in some cultures or even our past. Thanks for stopping by.

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  5. Didn't Teddy Roosevelt marry his first cousin? That law probably went into effect not long after that.

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    1. I think it was one of the Roosevelts that did that. I remember his wife didn't have to change her name when they got married. Thanks for stopping by.

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  6. Genetics is a fascinating field. I type some genetic reports here and there and it is always interesting when they do the family history to try to figure out where an anomaly could have come from. I have so many cousins I have not met since my mom came from a big family and everyone scattered that I often wondered could somewhere along the line a relative marry another relative and not know?

    betty

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    1. I have lots of cousins I haven't met too. Families really spread out in this modern world.

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  7. Just blah to siblings and even more blah to kid and parent. Cousins, I can see way back when you say they had little options, but now, blah. Although if you go far enough down the line, sometimes is could seem like you're related to everyone. With 160 you'd sure have to be careful of inbreeding. Plus, if you inbred too much, your skin can turn blue.

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    1. Blue babies, yep. Lots of cultures still do the kissing cousins thing. Thanks for stopping by.

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  8. Ew! I thought the rule was second cousins or farther apart? Maybe that's in Washington, or it's just something I was told. I love my cousins, but I would never consider them as part of a marriageable pool of people. I think the face that I'm between 6-12 years younger than some of my cousins and 3-13 years older than some of my cousins may have something to do with it. My only cousin near my age, well, he and I only agreed that playing pretend Star Wars was fun until we were 12. We bickered all of the time, and then, didn't really know what to think of each other after that.
    Sorry, had a TMI moment there.
    Minimum population - I think it has to be larger, like 300+. Maybe it's because I near-missed a major birth defect from one side of my family and I have two other genetically caused minor health problems, but I don't think I would want to be a part of a small gene pool.

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    1. Yeah, I think if someone had to select a small gene pool, they would weed out all of use with anything not perfect in our genetic makeup. Thanks for stopping by.

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  10. I really feel like GoT was setting us up - trying to force us to be okay with the whole aunt/nephew thing. After Cersei, nothing really seems as bad in comparison, but I'm still giving George RR a hard side-eye about everything. But I still get creeped out everything Mr. Collins asks Elizabeth to marry him in Pride & Prejudice. I get it, but why was that ever an option?

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    1. I totally forgot about Mr. Collins, but it does point out how common cousin marriages were not so very long ago. GoT really isn't doing anything the Russian Tzars didn't to. Still, very yucky for us.

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  11. Fascinating topic, Susan! With the mobility and overpopulation we have in the world today, I'd say it's best to stay away from any degree of family when marrying. In a future post-apocalyptic world with a small surviving population, I suspect all the rules, no matter how valid, would fly out the window.

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    1. So true. And it would only add to their problems. Thanks for stopping by, Patricia.

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  12. Congrats, Susan! I recently read an article that said 98 was a good minimum number for a viable population. Of course, more is probably better.

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    1. 98 seems pretty low. I thought 160 would be tricky. Thanks for stopping by, Cherie.

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  13. Fascinating subject! A real bottleneck occurred in human history during the last super volcanic eruption 70+ thousand years ago, only about 2,000 or so humans are estimated to have survived...so we're all a little related, I guess;)

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    1. We don't like to think about being related though, so we, Mark? LOL If we could all remember that, the world would be a better place.

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  14. Thanks so much for taking such good care of my blog while I was gone, Susan. It was a pleasure having you here. :) Congrats on the new book!

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  15. Inbreeding = yuck. So if having offspring with someone you're related to is so terrible, is the inverse true? Are couples who are from different races more likely to have genetically superior offspring then, because of the greater difference is genetics?

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  16. Hi Susan! Very fascinating post. As always. :) And the comment about Game of Thrones made me laugh. I hope your guest posts are going well. :)

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