Spider fear is there at birth, just like reflex to suckle a nipple, or pee when held away from mother momentarily. Evolution genetics in ancient tiny primates, still in our genes : **SPIDERS coded into brain neurons from genes, in womb**: *We Really Are Born With a Natural Fear of Spiders And Snakes, New Study Shows*: https://www.sciencealert.com/deep-unshakeable-fear-spiders-no-random-quirk-fate-born-arachnophobia *Itsy Bitsy Spider…: Infants React with Increased Arousal to Spiders and Snakes*: https://www.frontiersin.org/articles/10.3389/fpsyg.2017.01710/full happily, the list of encoded thoughts forced into humans is far far lower than any other animal. Even eating is merely a "habit" not an instinct. Seriously. Humans raised on medically delivered sustenance since birth have no "hunger reflex" to desire to eat food. The fact that spiders and snakes are still left in human brain at birth, along with yawning when others in burrow or den experience high CO2 levels (contagious yawning), is a puzzler. So much other preprogramming is stripped from Humans. Mating reflex (called "mounting reflex" in animal studies) is a primal instinct, but as seen in homosexuals and deviants, has a wide range of expressions. Want to know a far more ancient brain encoded thought ? Tens of millions of years old and still in brain.... **pre-wired smells!** ======== Genetically ALL ANIMALS are strongly attracted to a couple smells in incredible olfactory sensitivity: 1 > **the smell of damp earth** (sidewalk after it rains), to lead animals in deserts to puddles, the smell originates from bacteria and other than pheromones, is one of the most powerful detected scents in animals. https://newatlas.com/science/rain-smell-dirt-bacteria-geosmin-petrichor-evolution/ Animals have a second almost as powerful attraction... 2> **The smell of freshly broken or cut grasses**. Scientists think its a symbiotic survival tactic of plants to attract animals to locust swarms eating up a grass field. The smells entice animals to come and the reward are locusts (a locust is a fancy name for grasshoppers that mass into occasional swarms). jasmonic acid, and the aldehyde “Cis-3-hexenal” : https://www.scienceabc.com/nature/what-causes-the-fresh-cut-grass-smell.html So CUT GRASS and WET EARTH are among the most sensitive smells possible in mammals. Ovulation chemicals expressed in females (sweat below belly button in primates and above vagina) are also powerfully detected in science tests when a primate (including human) is ovulatiing (the point midway between two periods). According to research published in the journal Proceedings of the Royal Society B, women are actually most attractive to men when they're at their most fertile due to a special scent released by the body: *When women are at their most fertile time of the month, they SMELL BETTER to men*: https://www.independent.co.uk/life-style/health-and-families/what-men-like-women-ovulation-scent-more-attractive-a8533911.html Even strippers get up to 50% as much extra tip money when ovulating over a 5 day range. *Ovulating Strippers Make Bigger Tips*: https://www.scientificamerican.com/article/news-bytes-week-ovulating-strippers-bigger-tips/ Testosterone on the other hand is MILLIONS of times less powerful, but created in astoundingly high levels in males, so much so, a toxicologist might even quip that testosterone is a poison, due to its sheer volume. But Testosterone of course attracts all females ages 13 and up in soiled garment cotton swatch tests. **The smell of fresh blood!** If you were a carnivore predator you would also have a profound attraction to freshly spilled animal blood. So in order of smell sensitivity survival from above list : **WATER First, FOOD (insects) Second, REPRODUCTION Third sensitive smell**. Pre-wired in brain at birth. The three most powerful scents that motivate all mammals! Grass is second. Cut Grass!!!