I dont understand how instinct is transferred from parent to the child through genetics. How can a memory or behaviour be stored in genes? For example a snake has the instinct to hiss but how was that transferred from the parent to the child through genes? And how does it go from being just a genetic memory to actually go into the brain of the new animal and make them perform that behaviour?
You’re getting confused. Genetic memories, as depicted in works like Assassin’s Creed, aren’t a real thing.
A snake doesn’t necessarily have the genetic instinct to hiss. But it’s a thing it can do, it’s advantageous for it to do so, and it’s probably seen other snakes doing it. So it hisses.
I mean, think about the noises you make with your mouth. You weren’t born with the ability to speak your native language. You didnt interit it from your parents. You heard others around you speaking it, and picked it up.
Think of it more like hard-wired responses to sensory input. Prey animals which have their adrenal response triggered upon seeing movement in their peripheral vision were eaten less and thus procreated more. As a result, that species has evolved an instinct to run away or fight whenever a potential predator is nearby.
Likewise in your example with snakes, those which naturally felt inclined to hiss at potential threats were more likely to scare off predators and larger animals and thus not get eaten or stepped upon. Thus making them more likely to survive, procreate, and pass down genes with the same inclination.
Interestingly, it becomes a feedback loop. Animals which naturally stayed away from a hissing snake were less likely to be bit and thus suffer the consequences of snake venom. Again, making them more likely to survive and pass down those connections.
Hissing is a reflexive action. A startle reaction causes muscles to tense, air to leave past the vocal cords..a.nd a hiss comes out.
That hiss works, the snake starts to do it on purpose.
Take some things like building nests. The ‘instinct’ is things like an acuity to a certain visual stimulus, like crossing lines. And a perhaps a positive response to certain textures and tastes. So the animal grabs things that taste and feel good, and cross them over other things.
It’s often found that the first nests an animal makes aren’t very good. Prospective mates ignore them, or the animals nest falls apart and they loose their eggs. So the next year they try again, and genetically they tend to learn from this sort of behavior quite quickly.
Beavers are a great example of simple stimulus leading to complex behavior. Their entire dam building “instinct” seems to be a strong distaste for the sound of running water. They simply pile shit on top of the sound till it stops.
Researchers played such a sound through speakers on dry ground, and the beavers piled material on top of it, mud, branches etc.
This simple response leads to the entire submerged den ecosystem they thrive in.
Genome can contain instructions on how to connect neurons together – effectively “pre-programming” a part of the brain.
There is probably many different mechanisms of how it is done – but it looks something like this: one neuron has a “Beacon Gene” active, that releases some special signal protein. The other neuron has a “Seeker Gene” active, that produce a detector that detects that protein, and releases a growth signal protein. This makes the neuron cell to grow in the direction of the “beacon”, until they connect.
Note, that as far as we know, there is no reverse process. The memories cannot be “packed back” into genes. The child will inherit the instincts that their parent had at birth – but all their life experience after that is not inherited. All “genetic memory” must have originated in the genes in the first place.
I think there’s quite a bit assumed by the word “instinct.” The reality is that most of the behaviors we think of as inborn are actually partially learned and partially determined by environmental factors. While genetics might predispose an “instinctual” behavior to exist, that behavior might not be expressed unless there is adequate opportunity for it to develop in an environment. This link provides a good discussion of how our understanding of instinctual behavior has changed over the last century.