When the “D” speaks, we listen.
Welcome to the 12th edition of Discover Intimacy!
Read time: 10 - 12 minutes
We are finally wrapping up our four-part series on Sex at Dawn: How We Mate, Why We Stray, and What It Means for Modern Relationships.
Remember, the premise of this book is that monogamy is not a naturally occurring, biologically ordained practice. Authors Christopher Ryan and Cacilda Jethá take great pains over 300+ pages providing evidence to support their argument.
And, because you are committed to awakening your sexual intellect and subscribe to Discover Intimacy, you are now well versed in these arguments as well.
If you have not yet read previous editions of our four-part series, you can do so here: PART 1, PART 2 and PART 3.
Let’s begin.
WHY SIZE MATTERS
To understand Ryan and Jethá’s arguments in the section of the book that serves as the basis for today's post, we first must understand that biological traits and features provide evolutionary explanation for human behavior. Richard Potts, director of the Smithsonian’s Human Origins Program, states, “Questions of social life… may be accessible from studies of ancient environments, or from certain aspects of anatomy and behavior that leave material evidence.”
Which anatomy? What evidence?
Let’s start with the overall comparative size of men and women. The technical term for this is body-size dimorphism. Meaning, on average, what is the size difference between the average male and average female in a given species? Among certain species, males and females are nearly equal in size. Example: Gibbons. In others, males are roughly twice the size of females. Examples: Gorillas and orangutans. And yet, in others, males are roughly 10 – 20% larger than females. Examples: Chimps (our cousins), bonobos (more cousins) and humans.
Why does this matter?
“Among mammals, generally and particularly among primates, body-size dimorphism is correlated with male competition over mating. In winner-take-all mating systems where males compete with each other over infrequent mating opportunities, the larger, stronger males tend to win… and take all. The biggest, baddest gorillas, for example, will pass genes for bigness and badness to the next generation, thus leading to ever bigger, badder, male gorillas – until the increased size eventually runs into another factor limiting this growth.”
The other side of this assertion is that among species where males and females are the same size or relatively close to it (like humans), intense competition among males for females did not exist; which leads Ryan and Jethá, who contend that monogamy is not a naturally occurring, biological practice, to say that this lack of competition among human males means that multi-pairing among humans was the norm. After all, there is no need for two men to fight over a woman if both can have her. Simply wait your turn.
Now, a logical response to this argument would be that the biological evidence of sameness in size and lack of competition in fact supports that humans are naturally monogamous. After all, if we’re saying that human males have not been competing over human females for millions of years, couldn’t that be because they’ve been paired in monogamous relationships and had no need to compete with other males?
That’s exactly what researchers who disagree with Ryan and Jethá’s work argue. These researchers say that humans have largely been monogamous and potentially mildly polygynous (one man in relationship with multiple women). To this, Ryan and Jethá respond:
“Their analysis ignores the fact that the cultural conditions necessary for some males to accumulate sufficient political power and wealth to support multiple wives and their children simply did not exist before agriculture. And males being moderately taller and heavier than females indicates reduced competition among males, but not necessarily ‘mild polygyny.’ After all, those promiscuous cousins of ours, chimps and bonobos, reflect precisely the same range of male/female size difference while shamelessly enjoying uncounted sexual encounters with as many partners as they can drum up.”
OUTDOOR VS. INDOOR SPORTS
If you and your partner have ever tried to get pregnant and struggled, you know the process can be physically, emotionally and mentally taxing – to say the least. Getting pregnant is not easy. And, it’s not just because of advancing reproductive age in Western societies, daily stressors or imbalanced diets and lifestyles. Getting pregnant is difficult under even the best circumstances.
Our authors cite research stating that 35% of sperm are rejected within the first half-hour of intercourse. Women’s bodies perceive sperm as antigens (foreign bodies) and produce anti-sperm leucocytes, outnumbering sperm 100:1, to attack these foreign invaders. “Only one in 14 million ejaculated human sperm even reach the oviduct.” This is why people often refer to conception as a miracle.
Taking the process a step further is sperm competition.
“…sperm competition preserves the central purpose of male competition in his [Darwin] theory of sexual selection, with the reward to the victor being fertilization of the ovum. But the struggle occurs on the cellular level, among the sperm cells, with the female’s reproductive tract the field of battle.”
So much of our understanding of competition for mates is based on it occuring in the external, outside world.
Girl starts ovulating. Girl gets dressed in her most eye-catching attire and wears her most attractive perfume. Guy A sees her and wants her. Guy B sees her and wants likewise. Guy A begins to compete with Guy B for her attention. Guy A wins. Guy A takes her home where they have intercourse. Guy A impregnates Girl.
Excuse the dramatically simplified explanation, but we certainly understand how these scenarios develop. But what happens in a different scenario - where Girl has intercourse with both Guy A and Guy B within a relatively close timeframe and “the competition” occurs within her body?
“There is striking evidence that the female reproductive system is capable of making subtle judgments based upon the chemical signature of different men’s sperm cells. These assessments may go well beyond general health to the subtleties of immunological compatibility. The genetic compatibility of different men with a given woman means that sperm quality is a relative characteristic… ‘Females may benefit from sampling many males, and different females will not necessarily benefit from mating with the same high quality male.’”
Meaning, if we take our dramatically simplified scenario and apply this theory, Girl may go home with Guy A – a selection in the external world – but in fact, Guy B may be more immunologically compatible with Girl. Such that, if Girl had had intercourse with Guy A on Friday and Guy B on Saturday, Guy B’s sperm would have “won” and he would have impregnated Girl in spite of her external world preference for Guy A.
This research can be challenging for some – especially in the context of unwanted pregnancies that occur under duress. Are we inherently saying that the pregnancy occurred in those unfortunate situations because the woman’s body “wanted it”? The short answer is, we don’t know. Ryan and Jethá don’t address this conundrum in their work (and we can imagine why as it would be difficult to present this research while going down a potentially triggering and emotional rabbit hole).
WHEN "D" SPEAKS
On Jazmine Sullivan’s new album, Heaux Tales, are multiple interludes. In one interlude, a woman speaks about how she had a tumultuous relationship with her lover, but his dick spoke to her – specifically, spoke life into her.
Indeed, the human male penis is special. According to primate sexuality experts, “Adult male humans have the longest, thickest, and most flexible penises of any living primate.”
What would be the purpose of a penis so special? Going back to our earlier assertion that biological features and traits evolve as a function of behavior, there must be something about that dick.
And, there is – sperm competition. In a world where humans were biologically designed for multi-pairing (our authors’ premise throughout the book), the penis must perform some specific functions.
“The unusual flared glans of the human penis forming the coronal ridge, combined with the repeated thrusting action characteristic of human intercourse – ranging anywhere from ten to five hundred thrusts per romantic interlude – creates a vacuum in the female’s reproductive tract. This vacuum pulls any previously deposited semen away from the ovum, thus aiding the sperm about to be sent into action. But wouldn’t this vacuum action also draw away a man’s own sperm? No, because upon ejaculation, the head of the penis shrinks in size before any loss of tumescence (stiffness) in the shaft, thus neutralizing the suction that might have pulled his own boys back.”
This is rather sophisticated penile technology, proving highly useful in a multi-pairing environment where multiple males have sex with one woman and their sperm must compete for fertilization.
Ryan and Jethá summarize penile characteristics that support the theory of sperm competition:
"A penis designed to pull back preexisting sperm, with extended, repeated thrusting;
Less frequent (compared to chimps and bonobos) but larger ejaculates;
Testicular volume and libido far beyond what’s needed for monogamous or polygynous mating;
Rapid-reaction DNA controlling development of testicular tissue, this DNA apparently being absent in monogamous or polygynous primates;
Overall sperm content per ejaculate – in the range of chimps and bonobos; and
The precarious location of the testicles in a vulnerable external scrotum, associated with promiscuous mating.”
In summary, the dick was designed for a great deal of activity and even greater competition.
As we close our four-part series...
Is monogamy designed for humans?
Are we going against nature in its practice?
Are our sexual and reproductive lives best served by monogamy?
Based on our exploration of Sex at Dawn, we know what Ryan and Jethá would say, but what are your thoughts? Do you feel comfortable discussing this topic with your partner? Consider forwarding this post, invite him/her to read it and see how the discussion evolves.
We look forward to connecting with you in our next edition of Discover Intimacy.
