Eli5: how is it that so many species, including humans, have the same motherly instinct that suddenly appears after birth? Where does this come from?
In: 2
Survival of the species. Mothers who did not foster/protect their offspring had offspring that died and could not pass along the traits needed to have successful offspring. Basically, if your children cannot immediately take care of themselves after birth (like most fish and insects) and the maternal instinct to care for them until they can care for themselves doesn’t kick in, that genetic line ceases to exist because the offspring never reproduces.
If a species has babies rarely, they only have a handful of opportunities to successfully spread their genes to the next generation. The ones who protect that opportunity after it’s born get more surviving offspring on average. Over a lot of generations that means that the genes that make an animal instinctively protect their offspring become more and more common in the population.
It doesn’t apply to species that produce a lot of offspring at once (like fish) or can produce offspring every month or so for most of their lives (like rodents). It does apply to species that have a yearly reproductive season, and species that gestate their offspring for many months.
There are basically two very broad approaches to having kids, or “reproductive strategies,” in biology, called the “k” and “r” strategies. (Each species has its own life history, so this is simplified — in nature, there’s a lot of variation on these themes.)
R-reproductive species focus mainly on producing as many offspring as possible. These species include fish, mice, insects, etc. In these species, the main focus is just on producing offspring in large numbers, and then turning them loose at some minimally viable age. Yes, very large numbers will fail to grow up, but the sheer numbers make up for that.
K-reproductive species focus mainly on helping a small number of offspring succeed in life. These species include us, other large mammals, etc. Here, there are much smaller numbers of offspring, and a huge amount of effort is invested into trying to make sure they grow up and succeed.
Maternal or parental instincts are crucial to the “K” species, like humans. Evolutionary theory predicts that basic instinctive behaviors could evolve where they make it more likely for offspring to survive to reproductive age. Put simply, this behavior evolved because without it, “k” species like us would have trouble getting our kids to survive long enough to have their own kids.
For that to work as an explanation, our DNA must contain instructions to help shape the brain in a way that will make us feel good enough about parental behavior that we are willing to do it. That part is easily explained by evolutionary theory. So far neuroscience is not advanced enough to explain exactly how the brain structure works to make that a reality.
It is an instinct ingrained in our DNA. From the moment species started requiring mothers to take care of babies for the species to survive, the individuals with the more motherly genes/tendencies were more likely to keep their babies alive and pass on those genes. So over a long long long time you are left with only the individuals who have those motherly tendencies/instincts ingrained in their DNA.
The Three Fs: Fight, flight, and feeding.
Any organism that can’t do all three of these things will have lower offspring survival rate. Yours being an offspring.
Hormones. There are actually patenting hormones that flow through us not only after birth but when there is a small child around. Some have it more than others obviously buy that survival instinct is something hard coded into all animals.
At the basic core of any living organism, is the instinct to reproduce and create future offsprings to continue the species. That means the parent must have the drive to protect their some of their offsprings in certain ways that some of their offsprings make it to reproductive age.
Now, instinct is a complex behavior exhibited in response to certain stimuli. Our behavior comes down to chemical processes in the brain. So in response to certain stimuli (babies crying), it triggers a hormonal response in the brain to tend after the babies.
Now, where on our genome that encodes specific behaviors, is largely unknown,
Latest Answers