How could natural selection permit an animal to commit infanticide? If reproducing genes is the ‘goal’ of all evolutionary processes, how is it possible that some animals could kill their offspring, thereby ensuring that their genes are not passed on??
Does infanticide only occur in very specific situations, such as a major food shortage where both parent and offspring would die unless infanticide was performed? Does infanticide ever occur after the offspring has been weaned??
And what about infanticide in humans? Are there any specific circumstances that are typically present in cases where people kill their children, such as an underlying medical condition, or questionable paternity due to dissimilar appearance??
I would expect that mother-instigated infanticide is relatively rare and results from stressed or abnormal conditions of some kind. It’s always risked to try to assign “logic” to this sort of thing, but I’d imagine that it mostly happens when 1) the mother’s upbringing was abnormal in some way, resulting in less well-developed instincts (I’m not talking about humans here.) or 2) food, space, etc. is so scarce that the young would probably not survive anyway.
Step-fathers, human and otherwise are statistically more likely to harm or kill their mate’s offspring from a previous father. I think it’s quite common in situations where a dominant male lives with a group of females–lions, for example.
Female infanticide typically occurs in cultures where marriages and families are structured so that females are a cost rather than an asset. For example, in traditional Chinese families, where a girl goes to work for her husband’s family when she marries. I’m not aware of any culture where male infanticide is a widespread phenomenon.
In modern Wester societies, of course, there is the issue of abortion. It’s hard to know how to evaluate that, except to note that, perhaps for the first time in history, children are an economic liability, rather than an asset.
The Greeks and the Phoenicians were big into their infanticide - The Greeks for aesthetic / fairly superficial purposes - cf. Oedipus. The Phoenicians on the other hand used infants as sacrificial offerings to their Gods - hence the massive Phoenician infant necropolis outside Carthage - see
For the first stages of a sub-adult’s life, it consumes more than it produces, also, the parents must divert resources to the child.
Until the infant/cub/larva becomes an adult and starts producing for the benefit of the family/village/tribe/etc. the child is operating at a loss…and the powers-that-be may wish to cut losses when it suits them.
Basically, an equation (however conscious) of: Will my child-rearing resources be best spent on this child? Or should I focus my resources elsewhere (the child’s twin, a future child w/o sickness or deformity, a child whose father is known and approved of, a child born when we’re not in the middle of a famine)?
Hunter-gatherer groups also practice infanticide under conditions of deprivation. However, this is a personal decision which they do not undertake lightly, and parents often feel great regret years afterward.
Also note that children in hunter-gatherer groups aren’t really an asset until around adolescence. Before that, they don’t contribute anything that’s absolutely essential, though they do sometimes help in gathering plants and such.
Basically, infanticide acts as an error-checking mechanism to be sure that resources are spent on the best opportunity for passing on genes–which is a better genetic strategy:
(1) devoting inordinate amts. of time, effort, and food to raise a severely disabled child who will likely never care for himself, much less mate and reproduce, or
(2) killing said child early on, having a second (with luck, healthier) child, and focusing all of your efforts on her?
see the link. A number of reasons are given (uncertain parentage, child of first husband, wrong season–food shortage or mobility problem, presumably–mother died, child sick or deformed, etc.).
Among gorillas and chimpanzees, it’s common for males to come in, take possession of some females (although the chimps don’t really have harem-style groups…), and kill any offspring that the females already have (since they obviously aren’t his). This betters his chances over his competition.
Among humans, it was also because of co-sleeping back in the darker ages. Lack of birth control options meant a lot more babies were born, and co-sleeping (child in the bed with the parents) could lead to accidental (or semi-intentional) smothering.
This led to the rise of the laws to require the child to have separate sleeping quarters (moses basket, crib,cradle) and gave rise to a very expensive industry as well.
Now adays, co sleeping is safe, because we don’t ahve 60 million kids and as much entrapment or other social conditions … we have guidelines for taking care of the kidin the bed with you or next to you. So I should say, it’s safe when done properly (not alot of pillows, firm sleeping surface, no way for the kid to get between the bed and the wall, etc.
My sis and I had an intersting discussion on this I’ll see if I can dig up the book she referenced.
Mynn, what are you talking about? Isn’t Sudden Infant Death Syndrome unknown in countries where children sleep with their parents? That’s been the way people traditionally slept in many societies, and if it was killing so many kids, then parents would have stopped.
Male lions kill the cubs of a previous male in order to induce estrus in the females. The female lions will not allow mating or conceive while they are busy raising a youngster.
In general mother nature seems to prefer the survival of the adult over the offspring. An adult is a known success story and the baby is a question mark. An adult can have more babies at a later time but the baby will definitely not survive without the parent (assuming a species where parental care is a survival necessity). If conditions are such that raising a baby calls into question the survival of both parent and baby mother nature will push the parent to dump the baby and hope for better days down the road.
You can make a much better argument for all non hunter-gatherer societies, in which children are mostly useless until they get big. On farms, smaller children don’t do all that much useful work, though it makes the load a little easier.
Of cource, Post-Partum Depression should me mentioned. After a woman gives birth, her hormones fly out-of-whack in such a way that it causes her to go loco and kill her babies.
In various places on earth it is not uncommon that female babies are killed after birth. This has lessened somewhat in recent years due to a rise in use of ultrasound equipment to try and determine the sex of the baby in eutero.
Infanticide amongst mammals appears to be the ancestral condition. As far as anyone can tell all small mammals utilise infanticide from time to time. Most commonly this entails eating the young, but may employ simple neglect.
The why’s are very complex. Many mammals will eat there young simply out of stress. Something as simple as disturbing the nest will induce many animals to chow down on the kids. So ,no, infanticide doesn’t only occur in situations where both parent and offspring would die if it were not practiced. It would appear from this that the actual evolutionary penalty from infanticide is fairly small, since no more complex mechanism to avoid this unwanted killing has evolved. Presumably the trait prevents the mother potentially being ambushed at a later stage by a predator. The slight risk to the mother outweighs the more definite risk to the young.
Others have pointed out the circumstances surrounding much infanticide. It should be pointed out that the studies only examine socially sanctioned infanticide. It is suspected that most infanticide is not socially sanctioned and is kept hidden. It is impossible to know in pre-technological societies the numbers of parents who kill children ad then claim an accident.
Another point that must be considered is the effect of neglect. Most primitive societies practice what is essentially infanticide from neglect, particularly of female children. This would not show up on any study of infanticide. This is practiced in part because boys are more valuable. Another reason is that men in primitive societies suffer extremely high death rates. Without some comparable mechanism to check female survival the sex ratio would slip too far in favour of women.
Mynn, the example you gave was of deliberate infanticide, not accidental. The children weren’t accidentally smothered in their sleep–their mothers deliberately killed them.
You’ve also misread your sources. Look at what this excerpt from your first link says:
Translation: Having babies sleep alone isn’t necessarily the correct way of doing things, and having infants sleep with their mothers might actually provide important benefits. In fact, both articles list all sorts of good things to be had from having mothers and infants co-sleeping.
The second article also says that solitary infant sleep is an historical novelty, and that in the past, babies rarely slept alone. So co-sleeping isn’t dangerous, and in fact has been the norm for much of history.