The first law of biology is Malthusian superfecundity: All species produce more offspring than can survive. Humanity is not exempt.

I am pre-publishing this sequence of essays here and in social media to elicit comments and other feedback. They will form the framework for my next book, Darwin, Dada, Dalí, Duke, & Devadevàya.

Malthusian Superfecundity

Much of the European exploration of the New World can be traced to a single animal: the beaver. Because beavers are prized for their fur and the high-quality felt which is made from it, in many parts of North America the animal was hunted to near-extinction. Between 1901 and 1906, 10 mating pairs were reintroduced to the Adirondacks. By 1915, the population had grown to an estimated 15,000. If we conservatively calculate that all 20 were released in 1901, then each of the original beaver pairs produced 1,500 total descendants in just 14 years, with an annualized growth rate of 120%. With time, predators (including human trappers) limited their growth. If they hadn’t, starvation would have.

The potential for expansion is large with all living things. For instance, a mature female cat can have three litters a year, with 4-6 kittens each; if unrestrained, in 7 years a single female cat could produce 370,000 descendants. There are an estimated 75M house cats in the USA, most of which are not spayed or neutered. Probably none of them are reproducing at their maximum, but without some external agent checking their numbers, they could easily reach a trillion cats in a decade. Our animal shelters euthanize only about 1.4M of them per year, so clearly most cats die in other ways. If not, they would also die from startvation.

All living things are governed by the First Law of Biology. Malthusian superfecundity mandates that, unless some external force is culling the members of a species, all species will expand until they outstrip their food supply or other resources.

The First Law of Biology

I am certainly not the first to consider what might be the first law of biology. I found a paper which suggests that the first law should be, “All living organisms obey the laws of thermodynamics.” Although I appreciate the effort the authors put into their paper, I can’t go along with that. Thermodynamics is a physical law, it governs everything. Restating it in biology seems a redundancy. And besides, it misses why biology is a science, and why, therefore, it has the privilege, and the responsibility, to promulgate its own laws.

I found a philosopher who argues that drift—i.e. random biological success, basically dumb luck as opposed to superiority—is the first rule of biology. That argument is tantalizing. In later installments we will discuss why drift might be the most important mechanism in biology, but for the history of the science, Malthusian superfecundity is still the first law of biology.

I found a quantitative attempt to generate the first law of biology, looking at the tendency for variance and complexity to increase in biology systems. That is an important point, but below I will argue that variance is part of the the second law of biology, not the first.

In a thoughtful paper, a couple of scholars look at how we might generate biological laws from a theoretical perspective. They mention Mendelian inheritance, which I will also argue below is subsumed under the second law of biology. The authors, however, also suggest that biological laws should conform to the laws of the hard sciences: physics, chemistry, and perhaps, mathematics. As we go through these posts, I will suggest that there are good reasons that, not only does biology need its own laws, but the life sciences have injected new problems and solutions into biology, which not only begin to perturb the assumptions of the hard sciences, but also propose new considerations about how science works. So I do not think that the rules of the hard sciences are always appropriate, and so perhaps should not apply, in biology.

Wikipedia includes a list of laws and rules in biology. Oddly, Malthusian superfecuncity doesn’t appear on it. That seems strange, because without this law, biology isn’t even a science.

Malthus & Darwin

That’s because biology wasn’t a science until Darwin explained what Malthusian superfecundity meant for organic evolution.

Before Darwin, the ‘hard’ scientists often pooh-poohed biology. With good reason: up until On the Origin of Species appeared, biology was largely a gentleman’s hobby, the clerical pursuit of collecting and categorizing various specimens; and most of them dead specimens, at that. Biologists could offer no testable theories for their collections, and hence, they could offer no science. A lot of what those earlier naturalists offered instead were squabbles about how closely related two species might be. The 19th century English were just dotty about both collecting things, and social status. Since Victorian standing in the hierarchy largely depended upon how closely one was related the Queen and other noble families, at times their biological disputes seemed to eerily reflect their societal preoccupations.

Notice that they argued about how closely related various species might be. There is a common misconception that Darwin gave us the concept of evolution, i.e., the idea that different species comprising some group descended from common ancestors. For about a century before Origin was published, scientists were already actively discussing evolution. From both simple observation and early hints from the geologic record, 18th & 19th century scientists were pretty sure that, for instance, all cats were related, from the Lilliputian rusty-spotted cat (under 2kg) all the way up to the gargantuan sabertooth tiger (over 400kg). To become a real science, what biology needed was a working mechanism.

Darwin gave them their mechanism: Theory of Natural Selection.

But to get to that theory, Darwin had to start with the pivotal insight of the English cleric Thomas Malthus, who gave us Malthusian superfecundity: humans overbreed and outstrip our food supply. Darwin simply realized that this must be true for all living things. That provided him with the first postulate to the theory of natural selection, which I contend is also the first law of biology.

The second postulate from the theory of natural selection is the aforementioned variation within a species. Which is also where Mendelian genetics becomes important, because Mendel demonstrated that the variation, despite theoretical objections from some of Darwin’s critics, was real. Darwin realized that this variation in traits would result in a variation in competitiveness, and differential success in the struggle to survive and reproduce. So variation, in both traits and in survival, is the second law of biology.

The third law of biology is Darwin’s third postulate. Many of those advantages provided by variation would be inherited by offspring.

Those three postulates are actually biological laws. They are the theory of natural selection in a highly evolved nutshell.

When I teach freshman biology, I often ask if any of the students don’t believe in evolution. I then tell them I will present the theory of evolution in steps, and when I get to one they disagree with, they should object.

Then I list those three, pausing after each one and asking for objections. When I’m finished, I say, “That’s it, that’s the theory of evolution.” It saves me a lot of headaches, and gets some of their defenses out of the way.

Doomed Offspring

So an excess of offspring is not just a problem; it’s a law. Much as universal gravitation—and all universal forces—is a central law in physics, Malthusian superfecundity is the cornerstone of modern biology. And like any good law, it’s inescapable: all species exhibit superfecundity, they all produce too many offspring. And just as we might employ various counterforces to escape gravity, so might we also use an assortment of strategies to avoid Malthusian superfecundity.

But we never truly escape either. Or at least we haven’t so far.

The point we need to secure for our conversation going forward, the majority of offspring are condemned to failure and death. There just isn’t enough food and other resources to go around. In fact, this shortfall means that even those that survive will have a hard time of it. As we will see in the next post about death in the beauty of nature, almost no living things get to die of old age. That is also a key point going forward.

Malthusian superfecundity guarantees that the overwhelming majority of living things are doomed to a premature death. The sources of their deaths are limited to a few possibilities: starvation; injury and exposure to the elements; or predation. Most of those that die will succumb in childhood, many within minutes of birth.

Doomed Children

It is true of all species. Until the past century or so, this grinding suffering and early death were also true of humanity. That was the fate that Malthusian superfecundity originally described, that people must die. Throughout the history of humanity, most people died prematurely. As we noted in a previous post, about 75% of humanity died in each generation. Children made up the majority of those who succumbed.

It is difficult today, with our extraordinary luxury, to grasp this concept. It is difficult, and unpleasant.

It is, however, absolutely essential that we understand it. It does not matter if we can colonize the universe, it does not matter how much food we can grow on a square meter of soil, or even in satellites orbiting all the stars. There is a limit.

If we do not find ways to control population growth, we will outstrip our food and other resources, and then we will return to the horrors of history. We just don’t realize how close we are to returning to those hard, deadly times, nor how easily and quickly we could be in a situation where only some will survive.

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Picture of the Famine Memorial courtesy of Ron Cogswell.

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