“Male love circuits get an extra kick when stress levels are high. After an intense physical challenge, for instance, males will bond quickly and sexually with the first willing female they lay eyes on.Women, by contrast, will rebuff advances or expressions of affection and desire when under stress. The reason may be that the stress hormone cortisol blocks oxytocin's action in the female brain, abruptly shutting off a woman's desire for sex and physical touch.”

“Darwin theorized that mankind (both male and female) evolved alongside each other over millions of years, both reproducing after their own kind before the ability to physically have sex evolved. They did this through “asexuality” (“without sexual desire or activity or lacking any apparent sex or sex organs”). Each of them split in half: “Asexual organisms reproduce by fission (splitting in half).”

“During times of physical separation, when touching and caressing is impossible, a deep, longing, almost a hunger, for the beloved can set in. We are used to thinking of this longing as only psychological, but it's actually physical. The brain is virtually in a drug-withdrawal state. During a separation, motivation for reunion can reach a fever pitch in the brain. Activities such as caressing, kissing, gazing, hugging, and orgasm can replenish the chemical bond of love and trust in the brain. The oxytocin-dopamine rush once again suppresses anxiety and skepticism and reinforces the love circuits in the brain. From an experiment we also know that oxytocin is naturally released in the brain after a twenty-second hug from a partner- sealing the bond between huggers and triggering the brain's trust circuits.”

“(In actuality there are no such things as "male" or "female" hormones. Hormones have no sex of their own, and all types of sex hormones are present in all human beings in varying amounts.)”

“How does stress influence the midbrain pleasure circuit (or the feeding control circuits)? The short answer is that we don't really know. However, there are some tantalizing initial clues. Recall that twenty-four hours after a single exposure to cocaine, the excitatory glutamate-using synapses recived by VTA dopamine neurons express LTP. This change, which will result in greater dopamine release in VTA target areas, could also be produced by nicotine, mophine, amphetamines, or alcohol. Amazingly, even breif exposure to stress (a rat's five-minute-long forced swim in cold water) also produced LTP of the VTA synapses that was indistinguishable from that evoked by drugs. What's more, the stress-induced LTP could be prevented by pretreatment with a corticosterone receptor blocker. This suggests that drugs and stress rewire the pleasure circuit in overlapping ways and that the stress response to trigger LTP in the VTA requires a stress hormone signaling loop from the brain to the body and back.”

“The authors’ other argument is for the supposed social-bonding role of sex but how many ancestral males would choose to ‘socially-bond’ with a middle-aged or post-menopausal female when there are younger alternatives screaming out for ‘social-bonding’ elsewhere – young females who, according to Ryan and Jethá, were not letting their minds get in the way of all that ‘social bonding’. Back in the real world, as we have seen, the extensive human social networks are enabled by pair bonds, and our extra-marital sex is mostly about females acquiring meat or other resources and occasionally about men bonding by ‘sharing’ women for their own interests with little if any concern for female choice or female well-being.”