Infanticide and Cannibalism in Sociobiology

This is a little quote from E. O. Wilson’s Sociobiology that I deleted from the previous post for being a little tangential, but it is still interesting

Guppies (Lebistes reticulatus) are well known for the stabilization of their populations in aquaria by the consumption of their excess young.

So that’s what happened to my pet fish! I always wondered why they seemed to appear and disappear at random. It wasn’t a big enough bowl to logically be losing them in.

Um. Poor guppies.

“Cannibalism is commonplace in the social insects, where it serves as a means of conserving nutrients as well as a precise mechanism for regulating colony size. The colonies of all termite species so far investigated promptly eat their own dead and injured. Cannibalism is in fact so pervasive in termites that it can be said to be a way of life in these insects. …

The eating of immature stages is common in the social Hymenoptera.

Hymenoptera is an order of insects with over 150,000 species, including ants and bees. (Termites, despite also being social, are not members of hymenoptera, and are more closely related to cockroaches.)

Quoting Wikipedia:

Among most or all hymenopterans, sex is determined by the number of chromosomes an individual possesses.^[17] Fertilized eggs get two sets of chromosomes (one from each parent’s respective gametes) and develop into diploid females, while unfertilized eggs only contain one set (from the mother) and develop into haploid males. The act of fertilization is under the voluntary control of the egg-laying female, giving her control of the sex of her offspring.^[15] This phenomenon is called haplodiploidy.

However, the actual genetic mechanisms of haplodiploid sex determination may be more complex than simple chromosome number. In many Hymenoptera, sex is actually determined by a single gene locus with many alleles.^[17] In these species, haploids are male and diploids heterozygous at the sex locus are female, but occasionally a diploid will be homozygous at the sex locus and develop as a male, instead. This is especially likely to occur in an individual whose parents were siblings or other close relatives. Diploid males are known to be produced by inbreeding in many ant, bee, and wasp species. Diploid biparental males are usually sterile but a few species that have fertile diploid males are known.^[18]

One consequence of haplodiploidy is that females on average actually have more genes in common with their sisters than they do with their own daughters. Because of this, cooperation among kindred females may be unusually advantageous, and has been hypothesized to contribute to the multiple origins of eusociality within this order.^[15][19] In many colonies of bees, ants, and wasps, worker females will remove eggs laid by other workers due to increased relatedness to direct siblings, a phenomenon known as worker policing.^[20]

Another consequence is that hymenopterans may be more resistant to the deleterious effects of inbreeding. As males are haploid, any recessive genes will automatically be expressed, exposing them to natural selection. Thus, the genetic load of deleterious genes is purged relatively quickly.^[21]

Back to Wilson:

In ant colonies, all injured eggs, larvae, and pupae are quickly consumed. When colonies are starved, workers begin attacking healthy brood as well. In fact, there exists a direct relation between colony hunger and the amount of brood cannibalism that is precise enough to warrant the suggestion that the brood functions normally as a last-ditch food supply to keep the queen and workers alive. In the army ants of the genus Eciton, cannibalism has apparently been further adapted to the purposes of caste determination. According to Schneirla (1971), most of the female larvae in the sexual generation (the generation destined to transform into males and queens) are consumed by workers. The protein is converted into hundred or thousands of males and several of the very large virgin queens. It seems to follow, but is far from proved, that female larvae are determined as queens by this special protein-rich diet. Other groups of ants, bees, and wasps show equally intricate patterns of specialized cannibalism…

E. O. Wilson once said of Marxism, “Wonderful theory, wrong species.”

Nomadic male lions of the Serengeti plains frequently invade the territories of prids and drive away or kill the resident males. The cubs are also sometimes killed and eaten during territorial disputes. … Infant mortality is much higher as a result of the disturbances [in the social order of langurs.] In the case of P. entellus, [a langur species,] the young are actually murdered by the usurper…

 

 

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Homeschooling Corner: Science (geology and geography)

 

I have yet to find any “science kits” that actually teach science–most are just science-themed toys. There’s nothing wrong with that, but don’t expect your kid to re-derive the principles of chemistry via a baking soda volcano.

Smaller kids aren’t ready for the kind of thinking required for actual scientific research, but they can still learn plenty of science the mundane way: by reading. So here are some of our favorite science books/activities:

We did geology over the winter, centered around Rocks, Rivers, and the Changing Earth. It’s a lovely book (reading level about second grade?) with instructions for many simple experiments (eg, put rocks, sand, water in a glass jar and carefully shake/swirl to observe the effects of different water speeds on riverbanks) and handily complements any nature walks, rock collecting trip, or expeditions to the seashore.

WARNING: This book was published before plate tectonics became widely accepted and so has a confused chapter or two on how mountains form. SKIP THIS CHAPTER.

We also tried making polished stones in a rock tumbler (verdict: not worth the cost.)

After geology, we transitioned to geography with A Child’s Introduction to the World: Geography, Cultures and People–from the Grand Canyon to the Great Wall of China. I admit that geography sounds more like social studies than science, but it flows so perfectly from our understanding of geology that I have to mention it here.

I like to read this with a globe and children’s atlas at hand, so I can easily demonstrate things like latitude and longitude, distances, and different map projections.

With spring’s arrival we also began a study of plants and insects.

If you’ve never started your own plants from seed, any common crop seeds sold at the store–beans, peas, corn, squash, and most flowers–will sprout quickly and easily. If you want to keep your plants indoors, I recommend you get a bag of dirt at the garden center. This dirt is supposed to be “clean”; the dirt found outside in your yard is full of bugs that you probably weren’t intending on studying in your living room.

Speaking of bugs, we bought the “raise your own ladybugs” and butterflies kits, but I don’t recommend these as real caterpillars are nowhere near as cute and interesting as the very hungry one in the story. I think you’re better off just collecting ladybugs in the wild and reading about them at home.

The Way Things Work (also by this author: How Machines Work: Zoo Break) This is a big, beautiful book aimed at older kids, maybe about 10+. Younger kids can enjoy it if you read it with them.

Super Science: Matter Matters is a fabulous pop-up/lift-the-flap book about chemistry. We were very lucky to receive this as a birthday gift. (Birthday hint: the homeschooling families in your life would always like more books.) The book is a little fragile, so not appropriate for younger children who might pull too hard on the tabs, but great for everyone else.

Magic Schoolbus anything. There are probably several hundred books in this series by now. Who Was Albert Einstein? We finished our math biographies, so on to science bios. Basher Science: Astronomy  This is cute, and there are a bunch in the series. I’m looking forward to the rest. Professor Astro Cat‘s Atomic Adventure (also, Space!)