Sex Cells: The Evolution (or Design) of Genitalia
There’s been a lot of news about sex organs in recent days. Which does a better job of explaining the facts of life: design or evolution?
People either get squeamish or excited at the subject of genital organs, but we all live with our undercover parts every day and might respect them more if we understood what’s going on down under. Toward that end, we need to be able to talk about reality with the dispassionate demeanor of the physiologist. Then we need to consider how things got the way they are. So no prurience in this entry; just factual analysis of what science is learning about our so-called privy members. Much of the news (mostly about the male of the species, but some about both) is quite surprising.
Protein record: New Scientist reported research coming out of the Human Protein Atlas, a map of the human “proteome” (the set of all proteins made by the body). In “Amaze balls: Testicles site of most diverse proteins,” Andy Coghlan noted one unexpected result:
The proteins in our cells and tissues are responsible for everything from repair and maintenance to the production of signalling chemicals. You might expect that the brain, being our most sophisticated organ, would produce the widest array of proteins. But while the brain hosts 318 unique proteins that we know of, testicles are home to 999.
Many of those proteins are directly involved in sperm production and meiosis, the researchers found. “What’s going on in the testes is unique, as sperm must survive with half the chromosomes and outside the human body,” lead researcher Mathias Uhlén of the Royal Institute of Technology in Stockholm, Sweden, said. An article about this on the BBC News says that the “testes had more distinctive proteins because of their focus on producing large numbers of sperm without any errors in their genetic code.”
Uhlén expects that a similar number of proteins are made in the female reproductive organs, but “eggs are made inside fetuses, so he will not be testing this theory.”
Frozen: Must we lose the capacity to reproduce in limited years of youth? Medical Xpress reports that “Sperm grown from the frozen testicle tissue of newborn mice has been used to produce healthy offspring.” This offers hope to men scheduled to undergo surgery for testicular cancer “as a way of preserving their fatherhood prospects.” There’s also been talk of freezing female eggs as a job benefit for career women not wanting to lose their motherhood prospects because of work; Apple and Facebook recently were reported to be offering egg freezing to attract female engineers. Live Science published “5 Things You Need to Know” about egg freezing; though it’s better now than it used to be, it’s not guaranteed, it requires a lot of doctor visits, and it’s not recommended as a way of delaying pregnancy, Rachael Rettner warns.
Meiosis: The cell division process that yields sperm and egg cells with half the usual chromosome count is very complex. To keep the chromosomes from separating prematurely, the chromosomes must lock together tightly with molecular “glue”. The Stowers Institute for Medical Research identified a “molecular scissors” that separates the pairs at just the right time. The press release begins with admiration of the process:
The development of a new organism from the joining of two single cells is a carefully orchestrated endeavor. But even before sperm meets egg, an equally elaborate set of choreographed steps must occur to ensure successful sexual reproduction. Those steps, known as reproductive cell division or meiosis, split the original number of chromosomes in half so that offspring will inherit half their genetic material from one parent and half from the other.
The scissors is an enzyme named Topoisomerase II, “able to cut and untwist tangled strands of the double helix.” Without it, meiosis cannot succeed, and the organism (in this case, a fruit fly) is sterile. One of the researchers thinks the choreography is kind of messy and crazy. “This method of segregating shorter chromosomes may be clunky, odd, crazy, and as noncanonical as it gets, but that doesn’t matter, because the cells survive,” he commented. “In the end, these processes don’t have to be elegant, they just have to work.” And work it did, or he wouldn’t be here to say so. The article did not mention evolution.
Plant meiotic inversion: Plants do meiosis with a variation, a press release from the University of Vienna says. While describing it as an “orderly” process, the scientists found, surprisingly, that plants “show an inversion of the canonical meiotic sequence, with the equational division preceding the reductional.” Also, their chromosomes attach to spindle microtubules along their full length, rather than to distinct kinetochores, as in animal cell division. “These connections seem to provide sufficient force to allow proper orientation and disjunction during the second division, the article says.
Endowment: In an article beginning with a photo of two large brass balls, Lizzie Wade explained for Science Magazine why human testicles are much smaller than those of chimpanzees. It’s evolutionary, she says. First, the metrics: “Human brains are nearly three times larger than those of chimpanzees, but we’ve got nothing on our closest cousins in the testicle department,” she begins. “Whereas human testes top out at about 50 grams, chimpanzees’ routinely reach weights of 150 to 170 grams.” Why? It has to do with mating habits, she claims; primates like chimps that are more polygamous during mating season need more sperm-producing mass, while the more monogamous, like humans and gorillas, get by with less. Then comes the just-so story:
But hope is not lost, puny humans! Our primate ancestors appear to have switched between mating types—and, therefore, testicle size—at least six times before we came along, suggesting that testicle tissue may respond to evolutionary pressure more rapidly than other body parts do.
It’s not clear what Lizzie, a woman, wants to gain from bigger testicles in men. Is she advocating promiscuity? Men seem to do fine with what they have; the last thing one would think an evolutionist wants is a promiscuity-driven human population explosion. Incidentally, a survivor of testicular cancer is pushing a six-foot ball around the country as a “giant inflatable testicle” to raise awareness of the need for young men to be tested early, Breitbart News reported. Hopefully Lizzie Wade is not hoping for that level of “hope” for “puny human” endowments, or else the underwear industry would be cast into confusion, to say nothing of male athletics. Even with “puny” testicles, it’s quite remarkable the amount of motion that external male genitalia can sustain without damage during running and jumping sports.
Middle leg: Another popular evolutionary story making the rounds claims that the penis is a derivative of limb tissue. Another just-so story “Where the penis comes from” (Science Magazine) was echoed by Live Science (“How Sex Organs Get Their Start”) and another by David Cameron on PhysOrg, “Genesis of genitalia: We have one. Lizards have two. Why?” No one is claiming that lizards or humans fail in the reproductive act because of their equipment. Quite the contrary:
When it comes to genitalia, nature enjoys variety. Snakes and lizards have two. Birds and people have one. And while the former group’s paired structures are located somewhat at the level of the limbs, ours, and the birds’, appear a bit further down. In fact, snake and lizard genitalia are derived from tissue that gives rise to hind legs, while mammalian genitalia are derived from the tail bud. But despite such noteworthy contrasts, these structures are functionally analogous and express similar genes.
So what’s the evolutionary point here? No one is arguing that the “variety” works well in one species and poorly in another. It would make sense in a design view that functionally analogous organs would express similar genes.
In Science Magazine, Elizabeth Pennisi speaks more of functional design and health of sex organs, tacking on a short evolutionary story at the end. (Note to women: your anatomy is included in the discussion.)
It’s not a question a lot of scientists ponder out loud, but it’s key to much of life on Earth: Exactly how does the penis form? Today, two teams of researchers report having solved one part of this mystery, pinpointing how the organ gets its start in snake, lizard, mouse, and chick embryos. Now that they understand the penis’s origin, researchers can track its development in more detail to understand what drives it to follow a different path in females and become a clitoris. The finding doesn’t just answer a biological conundrum; it could also help millions of people born with genital malformations….
Regardless of this difference of opinion [about whether the specific tissues in the embryo are destined for limbs or genitalia], these new insights into how the penis gets started in the embryo are impressive, says Gunter Wagner, an evolutionary biologist at Yale University who was not involved with either study. “It’s seems like a pretty complete story to me.” For him, the work begins to address the question of how novel anatomical structures arise in evolution. And in that respect, he adds, “it’s a big advance.”
Most of the other reporters leapt onto the notion that the penis evolved from a limb. Live Science wandered into storyland:
“There’s always been a suggestion that limbs and genitalia might have co-evolved,” said Patrick Tschopp, a postdoctoral researcher at Harvard Medical School, who led the study. “When animals made the move toward dry environments, two things had to change.“
First, the earliest animals to crawl onto land hundreds of millions of years ago had to evolve limbs from fins so they could get around, Tschopp told Live Science. Second, the creatures had to find a way to protect their eggs and keep them from drying out. They were facing a much more hostile environment, and they could no longer just release their eggs and sperm into the water. Nature’s solution was internal fertilization — direct delivery from the male to the female, which required external genitalia.
Well, if “Nature” required it, then natural selection was there to produce it—that seems to be the suggestion. Thus, we have two SEQOTW winners in this post. Nevertheless, it is interesting that limbs and genitals share embryonic pathways. The BBC News reported that the scientists turned limb cells into genitals by switching certain genes on or off during development. This is not surprising, since the fates of many organs, including male genitalia, are switched on at set points during the embryo’s growth. That is why both males and females have nipples, which form before male genes are expressed.
Female mystique: The female reproductive apparatus came up in a New Scientist article. Reporter Kayt Sukel took issue with Vincensio and Guilia Puppo for publishing an article claiming to be the “final word” on female orgasm, saying that “the vaginal orgasm (and the G spot) does not (and could not) exist” and that the clitoris is simply a “female penis” with similar response to stimulation. “Female sexuality, including the female orgasm, is complex,” Sukel writes—too complex for such simplistic descriptions.
Origin of copulation: Evolutionists at Flinders University seem deliriously happy that the origin of sex has been “discovered.” In Science Daily‘s report, “Origins of sex discovered: Side-by-side copulation in distant ancestors,” the article was not really about the origin of sex at all (sexual reproduction was abundant in the Cambrian explosion and exists even among eukaryotic microbes). Rather, it’s about the earliest claimed example of internal fertilization, or copulation. It was inferred from fossils of “primitive” armored fish called placoderms. It’s not clear how the “origin” of sex fits the data, since internal fertilization was already up and running in these animals. “Our new discovery now pushes the origin of copulation back even further down the evolutionary ladder, to the most basal of all jawed animals,” they say—raising the question of how it evolved at all. Wikipedia laments, “The evolution of sexual reproduction is a major puzzle.”
Finagle’s 2nd Law states: “No matter what the anticipated result, there will always be someone eager to (a) misinterpret it, (b) fake it, or (c) believe it happened according to his own pet theory.” Darwin’s corollary can be stated: “No matter the phenomenon, there will always be an evolutionist eager to make up a just-so story about how it came to be.” It should be obvious from these news items that sexual organs and the processes going on inside them are out of reach of unguided natural processes. Genitalia, like every other part of the human anatomy, show profound evidence of intelligent design, from the macro to the micro level. Good grief; evolutionists have a terrible time explaining the origin of sex, let alone genitalia and the profoundly elaborate, irreducibly complex systems involved at every stage in baby making.
There’s been increasing openness in the media to discuss sexual organs. It’s becoming more common, for instance, for both men and women, including political commentators, to equate courage with having balls and cojones. Is that healthy? It’s certainly a big change from the prudishness of the 1950s and early 1960s. Laws about indecent exposure, and social norms about subjects considered improper for polite conversation help to protect women and children (men, too), from harassment and embarrassment. Leaked photos of nude celebrities recently produced an uproar in the media, with worries about privacy—a concept in retreat. Yet too much body shame can have negative consequences, too. People should be able to discuss genitalia in the right context with a certain level of emotional maturity. Everyone admires Michelangelo’s David, and most people have no qualms over nude sculptures in outdoor fountains in Rome and Washington DC. What should a creationist think?
In the 1970s, Dr. James Dobson—certainly opposed to indecency—nevertheless warned that shaming children who are inquisitive about their genitalia can be harmful to their spiritual development. He advocated nonchalantly covering up if a family member was caught in an unguarded moment, and speaking matter-of-factly about body parts in response to questions. Children are not naturally ashamed of nakedness, so the level of respect for privacy that is appropriate must be learned. Parents walk a fine line here. Christians and creationists believe we are “fearfully and wonderfully made” (Psalm 139:13-16) and that “everything created by God is good, and that nothing is to be rejected, if it is received with thanksgiving” (I Tim. 4:4-5). That doesn’t imply that everything created should be exposed or flaunted. Yet overreaction to body exposure seems discordant with the teaching that God’s designs are good and worthy of praise.
As with anything, the Bible is our guide. The Bible is not prudish about body parts, but is steadfastly opposed to lust and lewdness; it also associates nakedness with shame quite often (e.g., Rev. 3:18). Other than that, the amount of covering that is appropriate seems culturally determined to some extent. We are not to offend or take offense, but seek the good of our neighbor. And what is appropriate depends on context; beach attire is not appropriate in the office. Male-female differences must also be factored in. What’s at issue is not the body parts (which God created and pronounced “very good”), but the mind (which is fallen), and our responsibility to those around us.
Christians are understandably appalled at the lewdness of modern society. We have the opportunity to present a righteous standard, reacting but not overreacting. How do we teach and express a good balance? What has been your experience? Has it changed at all, the more you learn about the intricate design of sexual organs? Your comments are invited.
I recently read this book on embryology:
It blew my mind. It is somewhat technical but it does have a chapter on sexual dimorphism and almost no mention of evolution.