On the Survival of Humanity

This is some very basic biology: when resources are unlimited and there are no pressures on a species, its population grows exponentially. There’s also no evolution other than random mutations; without selection pressures (regardless of whether it’s natural or artificial), the genetic information content of a species doesn’t change appreciably.

Biologists make use of this to perform tests on certain cells. If you simply put a population of cells in a petrie dish and left them there, they start out by doing this:

They divide. They take over the dish. But then, they run out of room. And when that happens, they have to compete for the available resources. When resources get scarce, some cells are better suited to surviving. The better suited ones survive until reproduction, while the others die off. This is a very simple example of how evolution happens. Biologists often end-around this by taking a portion of the cells in a nearly full dish and transplanting them into a new dish before they run out of resources; doing this continuously keeps the cells from evolving.

Well, humans haven’t evolved much at all over the past 10,000 years (at least). But we have reproduced with amazing efficiency. In fact, there are humans pretty much everywhere on Earth. How has the human population grown? Exponentially. Take a look:

And now we have reached the point where the human impact on Earth has become significant. And we will soon (within the next 5 generations at best) be competing with one another for the resources of the Earth for survival, not just for profit. The current population density is 13 people per square kilometer, but as the population grows, more land needs to be designated for feeding that population. Take a look at our current population density:

Most of the world looks like it’s doing okay for now. But right now there are 1.3 billion people in China and 1.1 billion in India. Now, let’s consider only what will happen if population continues to grow, just in India, at the same rate it has grown since 1951. No social issues, no political issues, no ecological issues. By 2180, there will be over 31 billion people just in India, with a population density of 55 Indians per square kilometer of land on Earth. And by 2400, there will be over one trillion Indians.

My point is that Earth can’t sustain one trillion humans. If we don’t stop reproducing at an exponential rate, we will place selection pressures on humanity, and humans will either evolve or die off. And soon. But if we can keep human population reasonable, and the human impact on the planet reasonable, then we’ll be able to remain humans, and rule the planet, for as long as we like. I like this idea — let’s use what we know about evolution for good, and ensure the long-term survival and dominance of our species. (Plus, it gives us a big number to put into the Drake Equation!)


  1. #1 benhead
    March 25, 2008

    I believe most “expert” opinions (how can you be an expert on something that’s never happened? I dunno, ask a cosmologist predicting the end of the universe!) are that population WON’T continue to grow exponentially for very much longer. They do have some evidence to back this up, at least. China has already instituted population controls, but beyond that, there’s empirically little or no population growth in developed nations. China and India are rapidly developing, and while that’s difficult in terms of their already-large populations’ consumption of everything from oil to meat, it means once they come through they likely won’t keep reproducing like mad. Africa, of course, is the next potential trouble area, where the significant majority of the population is under 18 (obviously a sign of the high reproduction rate), and many nations are in dire straits with little chance of developing to a better state without help. I can recommend James Martin’s “The Meaning of the 21st Century” as a good book on all these issues. I don’t agree with everything he says, but I do agree with most of it, and it’s full of good insights. (Though I’ve seen a number of other books recently that look similarly good on the same sort of topics, that I haven’t had a chance to pick up yet.)

  2. #2 ethan
    March 25, 2008

    It’s a nice prediction, but in order to have a sustainable (i.e., constant) population, the average couple needs to have about 2.3 children. In India, at present, the average couple is having close to 5 children.

    I’m not arguing that we won’t do anything about it, mind you. China, Japan, and Europe are all either doing fine or taking measures to ensure that they will be ok. The US is fine as far as the middle classes and up, with poorer and non-English speaking constituents having higher rates. But if we keep reproducing and consuming resources at the rate we are, we are doomed to a crash.

    IMO, we are already overpopulated, and would do much better as a species if we had capped our population somewhere around half of what it is now. We didn’t, so now we have to deal with what we have. If we place selection pressures on humanity, we may become “more fit for our environment,” but we may also lose some things we value. If we lose our intelligence, that would be the worst outcome, to me.

  3. #3 benhead
    March 26, 2008

    Well, there are two ways to have a lower birth rate. Adult couples can have fewer children, or those children can die before they reach adulthood. And when we reach an absolute maximum of population, one or the other *will* happen. There can’t be 31 billion people in India, let alone 1 trillion. Not if they’re still going to need food and clean water. That much should be obvious. So the question is, which of the aforementioned methods will cause this levelling-off of population growth? And how do we go about ensuring that it’s the former, obviously vastly preferable one?
    It kind of sounds like you’re wagging your finger at people who choose to have more children. But the parts of the world where this is occuring are the ones where this is the absolute least of their problems. In the US and Europe, population growth has levelled off *because* we’re wealthy, because we value education and quality of life (and it’s hard to provide that if you have many, many children), because women have more freedom and choose to do things other than make babies, and for many other reasons. And China has enforced it with the power of a totalitarian government. India is currently a democracy, so they don’t have the totalitarian leverage, but it’s one where the bulk of the country is still impoverished. (Unfortunately I don’t have data on Indian birthrates in cities versus the countryside, but I suspect that the bulk of the problem is not in the cities [unless you include the shantytowns surrounding them].) And large portions of Africa have no effective government to speak of. It’s the root causes of these high rates that need to be addressed: improve education, give people lives beyond struggling to survive, eliminate violence in these areas, etc, etc. Then (contrary to what you might expect, now that I think about it) you might see this sitation improve.

  4. #4 ethan
    March 26, 2008

    I distinctly remember saying, “Now, let’s consider only what will happen if population continues to grow, just in India, at the same rate it has grown since 1951. No social issues, no political issues, no ecological issues.” It’s a strawman argument, to be sure, but the consequences of not addressing the evolution issue are what I wanted to state here. But yes, giving people something to strive for besides survival and reproduction hardly seems like a bad thing. 🙂

  5. #5 benhead
    March 26, 2008

    Oops, I did miss the lead-in describing it as an impossible hypothetical. Though I think the actual consequences of war and starvation are even worse, and may make an even more compelling argument. My point was just that you have to go a few steps further than telling people to stop reproducing, not least of all because the people reading this blog aren’t likely to be part of the problem.
    I’d also find it questionable whether evolution would play a key factor even in your dystopian future. Not only do societal and technological forces change too rapidly for an organism with a 20-year generational cycle to adapt to, but if there is, for example, a global food shortage, wealth (be it money or land or hydroponics equipment) will help an individual survive better than genes will.

  6. #6 DSingh
    December 21, 2008

    All this talk about population makes me wonder if world governments will think about culling the human population in response, we know how corrupt power makes us…

  7. #7 orlando hill
    January 9, 2010

    I don’t understand it. Why are people creating new babies Why are people growing in such big numbers. Have we not done these things before in the past (cooking, working, growing food). We will grow bored. Its like a chemical imbalance has affected all humanity and they are on a crash course to destroy the planet. God, you are so dumb. Do you not know that we cannot feed this many people for 100 years. There will not be enough land for food, there will be not enough fish in the oceans in ten years or air to breath with rainforest destruction. Why are you making so many babies!!!!!

    And all this for a freaking hamburger. yeah, real living. you have just depleted the world of living matter, and all that will be left are billions and billions of skulls of ugly humans.

  8. #8 Jim Jones
    March 16, 2010


    Well you have at least partially proved what the article talks about with evolution. You cannot stand to see that others (which i mostly assume are older) no nothing more than the innate imprint that humans have that reads “EAT SEX EAT SEX” If you are just one product of the population of which cannot ignore the problem (destroying the world), soon there will be generations and generations of whom will share your opinion (the evolution part). When people like this outnumber the “destroyers” now we have evloved into something else… as of now people like you are WAYY OUTNUMBERED by the “destroyers”… please wait….lol


  9. #9 crd2
    March 16, 2010

    Antibiotics are only for perscription, however several countries sell it over the coutner. If this continues our diseases will evolve beyond any know cure. Add this together with cancer, natural disasters, and AIDS & I think it will work itself out somehow.

    Countless times dominant species heve exploded in growth threating to dominate, like a Mr. Smith, through rapid reproduction. Until evironmental/biological annihilation dressed in a long black trenchcoat named Neo shows up and puts them in place.

  10. #10 Sphere Coupler
    March 16, 2010

    Neo is overdue…The only positive aspect of the massive population is the growth of knowledge.
    It could have been done with half the mass (of humanity) and better worldwide educational policies.

  11. #11 anna
    October 1, 2010

    I think that we know what kinds of people we can blame for this growing problem we are having. People like the octomom who wanted to have 14 kids. It should be illegal for a person to want to have that many kids. It is disgusting. I have a 3 year old boy and with god willing, I want one more and that is it. I don’s see how people can do that. The show on television called “19 Kids and Counting”. Why is this couple continuing to have more children? 19 kids? I don’t understand. I truly think that there should be a rule about having so many kids. It is not healthy. I also read a statement in which someone mentioned people in poor neighborhoods having too many kids. Why have kids when you cannot afford them? Young girls having children? What is wrong with our world? The population in India and China is ridiculous. I bet most of these people who are reproducing like crazy cannot even afford a decent life. There should be laws. It makes me so angry and sick to see people the octomom and other people on television reproducing like rabbits. That’s just stupid. I am sorry. I don’t want to offend anyone but its stupid.

  12. #12 crd2
    October 2, 2010

    I was watching a stand-up routine of a very crass comedian by the name of Bill Burr. His solution for population control was actually clever and hilarious.


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