Pleeblandia

Thoughts from the front lines


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The Scarcity of Human DNA

         Atwood’s finale to the MaddAddam Trilogy focuses on how the remaining group of humans survive the everyday struggles of a post-Flood world. This lack of survivors arises as a major issue for the survival of the human race, as their small number in size does not reach the minimum needed to viably repopulate the Earth.

         Back in 2002, anthropologist John Moore asked himself the following question: How many humans would it take to survive a 2000-year long trip to another solar system? In an attempt to solve this question, Moore postulated that a minimum of 160 humans would be sufficient to generate a stable and healthy population. More recently, anthropologist Cameron Smith tackled the same question and estimated that such a starship would have to carry at least 10,000 people.

         With this in mind, do the MaddAddamites and Gardeners stand any chance of keeping the human race afloat? Surely not. It’s pessimistic to say, but it is the harsh truth. For years, biologists have observed isolated animal populations whose numbers were initially incredibly low, like in the case of the platypuses (yes that’s plural for platypus) of King Island, found in the Bass Strait between Australia and Tasmania. A team of biologists sampled 18 individuals and found very little genetic diversity among them:

“Currently, genetic diversity in King Island O. anatinus is severely depauperate and the population is likely to be suffering from reduced fitness, reduced evolutionary potential, and an increased risk of extinction.” (Furlan et al., 2012)

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Simulated declining of genetic diversity among Kangaroo Island platypus populations. The black diamond represents the populations as of 2012. (Furlan et al., 2012)

The article offers solutions to this increased risk of extinction:

“To maintain adaptive potential and minimise the risk of extinction (Reed and Frankham 2003), levels of genetic diversity need to be maintained (in the case of Kangaroo Island) or ideally, increased. (…) Increasing the total population size through population range expansion can slow the loss of genetic diversity.” (Furlan et al., 2012)

Note: Kangaroo Island had the same problem as King Island. The study observed populations from both islands. 

         And so, the increasingly small group of MaddAddam survivors probably won’t be passing on the torch anytime soon. Unlike the platypuses of King and Kangaroo Island, humans can’t intervene and simply add more genetic diversity, and the survivors aren’t doing themselves any favors either. Not only did they off two Painballers with perfectly good DNA, essentially removing their genes from the gene pool, but Zeb also got himself killed on a trip out in the wild and indirectly caused Toby to die as well.

         4 humans down at the end of the novel, and the survivors are congratulating Swift Fox for having Craker babies instead of Painballer babies. It seems like Crake’s master plan worked after all. With human-Craker babies now in the mix, will the presence of human DNA in Craker populations drive the Crakers to suffer the same fate?

Read More:

Popular Mechanics – “How Many People Does It Take to Colonize Another Star System?

PubMed, NCBI – “How is extinction risk related to population-size variability over time? A family of models for species with repeated extinction and immigration.