Guest post for comment: sex and evolution

The following (below the fold) has been sent to me by Tam Hunt for comment by our readers. Constructive comment, that is. Tam’s own blog is here.

Absent-Minded Science, Part V: Sex, Psyche and Evolution

“The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!” Charles Darwin

Most people now realize that sexual attraction is in the mind, even though we often forget this insight in practice. The growth of phone sex and online sex is testament to the ability of imagination to titillate as much or more than actual human contact. And the presence of pornography in all cultures throughout history is an ongoing reminder that people can be turned on by the strangest things and certainly don’t need a live human being for this purpose.

There is a much deeper principle at work here, however; one that is highly relevant to this series of essays on “absent-minded science” (which is what I call the modern habit in a number of different fields of expelling mind from legitimate scientific explanations). Sex is central to human existence and other animals. But its centrality extends far beyond the animal world. This is the key theme of this fifth installment of this series.

Why is sex so central to our lives? The facile answer is that it’s because we need sex to reproduce. But this is only partly true. Many species reproduce without sex, including some complex vertebrates like lizards and fish. So why do we have sex? No one really knows the answer to this question, but there are many theories. I won’t delve much into why our species reproduces sexually; rather, I’m going to delve into what sex is, as a general principle, and the role of sex in evolution.

Natural selection is the key agent in Darwinian evolution. Natural selection is the label we give to the idea that traits that confer some reproductive advantage will obviously spread. But Darwin didn’t stop there. His second major book focused in part on sexual selection, another agent of evolution. “Sexual selection” is the bridge between Darwin and Lamarck and sexual selection is Lamarckian through and through. This is not generally acknowledged by today’s biologists and it may in fact be a novel interpretation. (Darwin was a Lamarckian in many ways, but this is not commonly known).

Sexual selection is the term Darwin gave to the idea that certain traits appear to be detrimental to survival and/or foraging for food – such as the peacock’s tail. However, if such traits help an organism find more mates and have more offspring the trait may still spread because its benefits outweigh its disadvantages. Mate choice, primarily female choice because males are generally the aggressors in most sexually-reproducing species, is key to sexual selection.

Natural selection is supposed to be a general theory of evolution, which means that it should be applicable in all times and all places and tell us something about how and why populations and species evolve.

To be a general theory of evolution, however, it seems that a theory must possess at least the following features: 1) applicability in all times and places; 2) capability to make predictions that are testable; 3) falsifiability, which means that if predictions are tested and found to be false then the theory as a whole may eventually be rejected under the weight of sufficient counter-evidence.

Sexual selection is arguably a more general theory than natural selection. Historically, these two selective forces have been presented by biologists as parallel forces, but with natural selection as by far the more important force. In reality, of course, there is no “force” behind natural selection. It’s just physics and chemistry in action, so when we talk about natural selection as a force or an agent, it’s reification of a sort at work. Rather than being an actual force, natural selection is just a label for the collective forces of nature acting on organisms with various traits.

Sexual selection is different, however, because there really is supposed to be a selective agent (a force of a sort) at work, which may not be explained wholly through physical and chemical forces – if these forces ignore mind in nature. This goes back to Parts I through IV of this series of essays, however, because contemplating these ideas requires that we consider whether mind (and thus choices made by minds) can in fact be explained through current physical and chemical theories.

I argued earlier in this series that current physical theories cannot, in principle, explain mind because the constituents of matter are defined by modern physics as wholly mindless. We are thus left with a system of physics that excludes that which is most real to each of us – ourselves, our own minds, subjectivity itself – which surely should be included in an adequate theory of physics and, by extension, biology. I argued that this impasse requires the inclusion of mind, in a highly rudimentary form, in all forms of matter, a view known as panpsychism or panexperientialism. Panpsychism holds that as matter complexifies, the tiny bit of mind in each tiny piece of matter complexifies and eventually reaches our highly complex type of mind due to the highly complex matter that comprises our brains and bodies.

This begs the question: how did we, and other life forms like us, reach such a high level of complexity? How did we evolve? This is where evolutionary biology and the philosophy of mind intersect.

If we acknowledge that all matter has some degree of mind, no matter how small, we realize that choice must be inherent in all matter. This is the case because the essence of mind is the selection (choice) between alternatives made available through perception. One of today’s preeminent physicists, Freeman Dyson (Professor Emeritus at Princeton’s Institute for Advanced Study, the same institution where Einstein resided for a number of years before his death in 1955) makes this point explicit: “[T]he processes of human consciousness differ only in degree but not in kind from the processes of choice between quantum states which we call ‘chance’ when made by electrons.”[i]

Dyson is saying that what physicists normally interpret in electron behavior as pure chance – randomness – is better interpreted as choice. Choices can be fickle, so what seems to be random is in fact a result of unpredictable choices by these tiny entities. Thus, even electrons make choices – but very very simple choices compared to the infinity of choices possible to our advanced human consciousness. Choice at the level of the electron is apparently limited to how the electron will manifest and move in the next moment. Particles such as electrons are not static, timeless entities. Thinking of the fundamental constituents of reality as unchanging particles is the fallacy of “substantialism,” which Whitehead’s panpsychist “process philosophy,” attempts to correct.

If choice is inherent at the level of electrons, a universal principle of evolution is made apparent. I call this universal principle “generalized sexual selection.” The essence of sexual selection is choice – generally female choice, as Darwin described in his 1871 book, The Descent of Man. Darwin recognized that many traits, such as the peacock’s tail, could not be explained strictly through natural selection. Rather, Darwin argued that female choice resulted over many generations in pronounced features in males who compete vigorously for female attention.

To be entirely clear, the peacock’s tail is not considered adaptive because its weight and size make it harder for male peacocks to escape predators and to forage for food. But if its disadvantages are outweighed by increased mating opportunities for the male who carries the showy burden, it will continue as a trait in male peacocks.

Darwin’s division of natural selection and sexual selection into two distinct agents of evolution, which continues to this day in biology, is not, however, warranted when we think through the better interpretation of what’s really going on.

The simple structure of neo-Darwinian natural selection has just two parts: 1) random variation of traits results from random mutation of genes and through sexual recombination; 2) those traits that confer a survival and reproductive advantage will obviously increase and are thus “selected.” (Again, there is not really any “selection” going on, but the end result is “as if” there was some selection process).

What I call “generalized sexual selection” (GSS or “giss”), re-frames this argument as follows: 1) variation in traits comes about through random mutation and through male competition for mating opportunities and striving more generally for self-improvement, which can sometimes be incorporated into the germ line of the male[ii]; 2) female choice is the selective agent that leads to greater reproduction of those males with the most desirable traits to the females who choose them, who incorporate the male germ line into their own by mating with them. In other words, variation is not always random – it is sometimes directed, with increasing mating opportunities as a significant motivation, and the urge to survive and other urges surely at work also. Perhaps more importantly, selection is not blind, it is conscious at every level of nature through the choices made mostly by females.

I call this theory generalized sexual selection because it applies to situations that don’t involve sex in the traditional sense. Most species on our planet don’t reproduce sexually. Bacteria, for example, often reproduce asexually, as do protists. And even many vertebrates reproduce asexually, such as certain species of lizards and fish. However, bacteria are constantly exchanging genetic information, which is a rudimentary kind of sex, defined at this level as the mixing of genetic information from at least two entities. This type of sex is known as “horizontal gene transfer” because it occurs without simultaneous reproduction.

But here’s why GSS applies beyond traditional sexual reproduction. The terms “male” and “female” are not as clear-cut as we generally assume. And in GSS, “male” refers to any genetic donor and “female” to any genetic recipient – as Lynn Margulis and Dorion Sagan describe in their 1986 book, The Origins of Sex. Thus, a bacterium that gives some genetic material to another is a male and the recipient is a female. These roles can and do change on a regular basis, thus the “gender” of each bacterium changes regularly. What is important, then, is not gender, per se, but actions.

The principle extends even deeper, however, when we consider further the panpsychist notion of matter. If all matter has some degree of mind or subjectivity, then GSS applies to literally all matter, not just biological forms. This is the case because the most sophisticated panpsychist thinking, that of Alfred North Whitehead and his intellectual descendants, recognizes that each of the ultimate constituents of matter – what Whitehead calls “actual entities” – contains both “mental” and “physical” aspects. They are two sides of the same coin. Physical and mental aspects of each actual entity (the Whiteheadian “atom”) oscillate with each step forward in time.

The mental aspect of each actual entity is informed by the immediately prior physical aspects of all other actual entities available to it. Each actual entity, in its mental aspect, chooses what information to accept and rejects everything else. Thus, the mental aspect of each actual entity can be considered to be “female” insofar as it chooses what information from the universe around it to include in its objective manifestation – like the female bower bird accepting the attention of a hard-working showy male. When the actual entity becomes objective, it becomes “male” insofar as its manifestation now constitutes information for the next round of actual entities to consider in their mental/female aspect. More crudely put, the female aspect receives and the male aspect penetrates. But these aspects oscillate within each actual entity.

Wipe your brow as I wrap up this essay.

GSS is a powerful re-framing of evolution in a way that recognizes the unbroken continuum of the complexity of matter, which is experiential through and through. I won’t delve into further details about the testability and falsifiability of GSS here, but it is my view that GSS presents a more adequate theory of evolution than the prevailing adaptationist view of natural selection – which generally denies the role of mind and choice in evolution.

Who knew sex was so important?

My next installment in this series will explore the current view of natural selection as the key agent for evolution, and its problems, in more detail.

Tam Hunt is a philosopher, lawyer and biologist. He lives in Santa Barbara and keeps a blog, Thought, Spirit, Politik at www.tamhunt.blogspot.com.

Notes

Filed under: Evolution, Guest post, Science Tagged: Evolution

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