This is the only science textbook to win a Pulitzer!
Ants are only ~20% of human biomass, not 100% as the book claims, but that's 2.5m ants per human!
Sterile ants, which are all female, help the queen reproduce instead of having their own kids.
- Ants, bees, wasps, etc. are haplodiploid, i.e. females have father + mother genes, males develop from unfertilized eggs (only mother genes).
- So, sisters share 75% of genes, more than 50% with their own kids. Helping mothers make sisters is better than having kids!
- (And if this isn't an alien civilization, what is? We don't need sci-fi. Nature is weirder than fiction.)
But their math doesn't hold up!
- If the queen produces 50% brothers (with 25% common genes) and 50% sisters (75% common genes), the average is 50% common genes, same as having kids.
- But building a nest is hard, specialization is efficient, etc. So ants stay sterile and help the colony.
- BTW, this gene math only works if the queen is 100% monogamous - so they are, or at least, were, until evolution locked it in.
- (Making nature one-step less alien. But still weird.)
Epigenetics determines caste. More food or specific food (e.g. royal jelly in bees) changes gene expression of the same DNA.
- When a queen dies, some ants (e.g. Indian jumping ants) can reprogram a worker ant into a queen through diet!
Leafcutter ants have been "farming" for 50 million years. Rather, are part of an agricultural symbiosis.
- They cut leaves and feed it to a fungus they cultivate in their nests.
- They protect the fungus from pests using antibiotics produced by bacteria living on their bodies. They clear decay and weeds.
- They can't live without the fungus because it produces a nutrient (Arginine) that they need but can no longer make themselves.
Ants communicate using pheromones, touch, and sound.
- Pheromones can communicate species, colony, caste, reproductive status, alarm, food trail, etc. These evaporate unless reinforced.
- They have a bigger, more advanced, brain region than other insects. It's not multiple brain parts coordinating.
- Using CRISPR to knock out pheromone receptors makes ants unable to communicate. Mutant ants wander aimlessly until killed by the colony.
- They tap each other with their antennae: to taste skin for identification, or to beg for regurgitated food.
- Some ants have a scraper on their waist that they rub against their abdomen. Triggers "emergency alarm", e.g. "I'm buried" or "Help me cut!"
Ant colonies are superorganisms, i.e. agents that work together to produce emergent behavior. They have sterile castes. Only ants, bees, naked mole rats, ... qualify.
- The nest is like a giant lung. Passive ventilation sucks CO2 from top chimneys and brings in O2 from lower entrances. They regulate temperature by opening/closing nest entrances. They send workers out for water to evaporatively cool the nest.
- They circulate nutrients by vomiting food into each others mouths. (Ants have two stomachs - one for themselves, one for sharing.) Ants can't digest meat but larvae can, so they feed meat to larvae and share the digested food. Larvae act like a liver.
- They have an immune system. Sanitation squads carry dead ants far away. Fungally infected ants leave the nest and die alone. Infected pupae are killed by workers.
- They have a neural system. Memory is stored in pheromone trails.
Ant politics exists. E.g. Workers destroy eggs laid by other workers, protect sister-laid eggs, etc.