The Chemistry of Human Nature

Tom Husband

• Publisher: Royal Society of Chemistry
• Year: 2020
• ISBN:
  9781839162954
• Edition: 1
• Topic: Ciencias biológicas
• Subtopic: Bioquímica

Why does chocolate taste so good? Why do we seek 'the one'? How do traits such as intelligence, creativity and violence arise and what purpose do they serve? This book links these characteristics to the origins of life, showing that the conditions necessary to bring life into existence echo through our modern day behaviour.
The chemistry of the body is not only fascinating but also highly relevant to everyone, since we are all concerned with maximising our health and enjoyment of life. Currently, there are not many popular science books concerned with biochemistry. One reason for this might be the particularly complex nature of the science involved. This book starts with the fundamentals and then works towards a deeper understanding of the chemistry of human nature. Essential reading for anyone with an interest in this science and written at a level accessible to experts and non-experts alike.

Section 1:
Fuel and Building Supplies

CHAPTER 1

The Chemistry of Space Travel

One day in April, 2013, my students burst into my classroom clamouring about something utterly incomprehensible—a group of individuals had volunteered to take a trip to Mars. This fact alone did not quite account for the levels of consternation they were demonstrating, until one of them excitedly added: “They're not coming back! They've said they'll go to Mars but that they'll stay there.” They had learned on the news about the Mars One mission—a voluntary, one-way trip to the Red Planet open to non-professionals. This was not one of those adult preferences I could explain by assuring them they would understand when they were older; I was just as flummoxed as they were.

Two connections with the origins of life occurred to me, one immediately, the other much later. Mars is in the habitable zone of our solar system, meaning its conditions could potentially support life. Martians have been a rich theme for sci-fi and now these Mars One astronauts may get the chance to seek actual evidence of their existence. But could there be another connection? Could it be that the manner in which life emerged explains the baffling motivation of these volunteers?

This book will present the case that the unique conditions necessary for life to originate are echoed throughout our modern-day behaviour. The central role of eating in cultures around the world, our romantic search for The One, our social tendencies and our craving for success can each be understood in terms of the thermodynamic demands of the chemical reactions that launched life. But how compatible are these traits with a suicide mission to Mars?

1.1 IS IT IN OUR NATURE?

What can the intentions of the Mars One hopefuls tell us about human nature? Homo sapiens have been explorers since we left Africa to colonise the world and perhaps before. But we are also social creatures inclined to live in communities and raise families.

The aims of the Mars One hopefuls may or may not be representative of human nature. More than 200 000 people applied for a place on the mission¹ and, in February, 2015, a shortlist of 100 candidates was published.¹ A gruelling training program will serve as the interview process, whittling that number down to 10 successful candidates—the intrepid individuals who will leave behind their friends, family and atmospheric oxygen in order to settle permanently in extra-terrestrial environs. Certainly, the number of applicants is large, but it forms a miniscule proportion of Earth's population. We can only speculate on what proportion of those applicants would actually go through with the mission if they were selected. If 10 volunteers actually depart for Mars, their actions will not be necessarily demonstrative of human nature.

What their actions might tell us about human nature requires consideration of what human nature is. The following is a proposed list of universal human traits compiled by George Peter Murdock:

Age-grading, athletic sports, bodily adornment, calendar, cleanliness training, community organisation, cooking, cooperative labour, cosmology, courtship, dancing, decorative art, divination, division of labour, dream interpretation, education, eschatology, ethics, ethnobiology, etiquette, faith-healing, family, feasting, fire-making, folklore, food taboos, funeral rites, games, gestures, gift-giving, government, greetings, hairstyles, hospitality, housing, hygiene, incest taboos, inheritance rules, joking, kin-groups, kinship nomenclature, language, law, luck superstition, magic, marriage, mealtimes, medicine, modesty concerning natural functions, mourning, music, mythology, numerals, obstetrics, penal sanctions, personal names, population policy, postnatal care, pregnancy usages, property rights, propitiation of supernatural beings, puberty customs, religious rituals, residence rules, sexual restrictions, soul concepts, status differentiation, surgery, tool making, trade, visiting, weaning and weather control. (Reproduced with kind permission from Columbia University Press.)²

These traits can be divided into four interconnected themes: safety in numbers, eating, mating and status. Four traits are directly linked to eating, whilst six relate to romantic union and the potential it provides for reproduction. Roughly half of the characteristics could be categorised under safety in numbers. For example, body adornment denotes clan membership, the hope being that the person dressed like you will fight alongside you if outsiders attack. Publicly observed customs on hygiene promote safety through good health, while collective agreements, such as governance, law-making and property rights, assure security. The status theme is only directly linked with the trait of status differentiation, but it influences many of the others. High status predicts superior access to food and mating opportunities, along with greater means to preserve the wellbeing of one's kin. Moreover, educational attainment is a common indicator of socio-economic status, religious rituals typically produce religious leaders, etiquette incorporates deference and so on.

1.2 A REACTION OF SELF-REPLICATION

All of these traits also have something to do with wants. Athletic sports are only interesting because the athletes want to win. We want to spend time with loved ones and when their demise makes that impossible, we mourn them. We observe laws because we want to be treated fairly. We observe certain customs because we want to stay healthy. We use tools to make things we want, and use trade to get things we want.

The fascinating thing about our wants is that we are made of atoms that do not want things. As we will see in Chapter 4, this situation seems to have arisen from the emergence of a very special kind of molecule, which has the ability to make copies of itself. These self-replicating molecules were the first ancestors of our modern day DNA, which now feverishly produces copies of itself. These long molecules are like necklaces composed of four different beads, with the twist that each bead is exclusively attracted to one of the other three. As such, a completed necklace will attract nearby, loose beads to line up next to it in a sequence that exactly mirrors it. When the mirror image spirits yet more beads to line up alongside it, the sequence of the third necklace exactly matches the first. In the same way, these self-replicating molecules were made up of four different units called nucleobases, which also form exclusive pairings.

Scientists have long puzzled over how to resolve this replicative activity with the laws of thermodynamics, seemingly fundamental rules of the universe that favour chaos over order. Our bodies are phenomenally ordered, notwithstanding the chaos we use them to create in the world. As such, the ongoing chemical self-replication that sustains life has been called a far-from-equilibrium state, which depends on the constant supply of two things: fuel and building materials. Provided self-replicators maintain this constant supply, they can keep replicating.

Now let's imagine two self-replicators, one short and one long. The short self-replicator will be able to copy itself more quickly than the long replicator. The replica of a self-replicator is itself a self-replicator, and once the first replica is complete, it will start making new copies of itself. Before the long replicator has finished a single copy, its rival has multiplied into two, both of which are now copying themselves again. If the building materials and the necessary fuel are in finite supply, the long self-replicator will eventually go out of existence.

Two developments follow. First, the self-replicators make mistakes. Sometimes they produce an unfaithful copy, where the wrong “necklace bead” gets added to the chain. This can lead to the production of faster self-replicators that will outbid their peers for the finite supplies. Second, the self-replicators start to act as instruction manuals for how to make other molecules called proteins. Again, some of these proteins may be a hindrance, but others will help the self-replicators to compete for the limited resources available.

These two facts trigger an arms race. Copying errors can help the self-replicators to reproduce more quickly, but these molecules also code for the production of proteins. What happens when the instruction manual makes an unfaithful copy of itself? Then, following the instructions produces a different outcome. When self-replicators make shoddy copies, new proteins are invented, some of which will be helpful and others a hindrance.

The arms race escalates. The self-replicators constantly modify their operation and those that improve their efficiency breed their rivals out of existence. They stumble over a recipe to build the protective casing we now call a cell membrane. These membranes act as filters to absorb useful substances and keep out harmful ones. These emerging lifeforms develop molecular motors to help them move. They evolve linking proteins, with which they reach out for each other and form mutual alliances. Cell types diversify, enabling division of labour. Organisms grow and they learn to transform sunlight into fuels, send tendrils burrowing into the earth to extract minerals and grow leaves to harvest the sun's rays. Anything that helps the self-replicators better compete for the finite resources of fuel and building materials swells their production of replicas. Meanwhile, newly forged replicas tumble off the production line, equipped with the same set of tactical advantages.

A huge breakthrough was the evolution of pleasure. Evolving combinations of new and old proteins formed brains that could direct the activities of the organism. These brains worked by expressing their approval, rewarding host organisms with a pleasurable sensation when they helped their self-replicators to get what they want. Eating food earns a reward because it supplies fuel and building materials in the form of nutrients, such as sugars and proteins. Mating earns a reward because it produces new vessels in which for self-replication to continue after the old vessels have died. Now, as before, atoms do not want things and self-replicators made of atoms do not want things, but they have succeeded in forging an intelligent, protective casing that does want things, and it wants not for itself but for its self-replicators (at least until humans appeared).

Our wants begin to make sense in light of the needs of the self-replicators. We are rewarded for eating as it provides the energy and protein necessary to replicate the DNA into which those ancestral self-replicators have evolved. Sex is pleasurable because we are rewarded for actions likely to produce children, the new vessels in which for self-replication to occur. We are adapted to cooperate so as to improve our safety, as well as to spread the risk of maintaining the food supply necessary to keep us alive. Meanwhile, elevating our status increases our access to food. Being overweight became a status symbol in post-revolutionary China, signalling that you could afford to eat well (on the frequent occasions that I was called fat when I lived there, I was assured it was a compliment for this reason). Status also improves our chances in the dating game, enabling us to select mates that represent the best long-term chances for the continued self-replication of our genetic material. If there is one thing peacocks have taught us, it is that bling gets chicks.

1.3 A RISKY STRATEGY

Universal human traits reflect the needs of the self-replicators, but do the actions of the Mars One volunteers make sense in the light of those traits? At face value, a one-way trip to Mars is a risky strategy to guarantee the continued replication of their genetic material. But then, the way things are going on Earth, the greater risk might be to stay put. Do our wants still reflect the needs of the self-replicators?

1.3.1 Eating

One of the Mars One hopefuls, Leila Zucker, has said that the hardest thing to give up would be her husband, followed by meat.³ In her shoes, I would be worried that there will not be anything to eat at all: permanent emigration to a barren planet is not the last word in food security. But the would-be colonisers will need to eat and the great challenge of doing so will merely heighten the focus. If they want to live on Mars, they will have to pioneer a sustainable means of food production. Assuming the organisers secure enough funding to run the mission, presumably a sizeable sum will be available for this critical requirement. So, while a trip to Mars does not guarantee access to nutrition, it is guaranteed that considerable effort will be made to meet this need.

1.3.2 Reproduction

This is where things start to fragment. A one-way trip to Mars may or may not represent the best mating strategy, but the best mating strategy may or may not represent the motivations of the candidates. The strategies evolved by the self-replicators often drive us to commit actions that are no longer of any service to them. When we consider how they influence our behaviour, we hav...