Tag Archives: natural selection

Pandemic 03: Survivability Traits

by Shane L. Larson

Over the millions of years that natural selection produced modern humans, countless traits were selected becasue they were somehow advantageous to our suvival. Ultimately, some 40,000 generations ago, modern humans began walking the lands of Earth; experiments that Nature had made as it grew our branch of the Tree of Life were terminated without a second thought. Today, there are no archaic humans left — gone are those that came before us, erased but for a few fragments and bones that rise from the tomb of the Earth.

A skull of homo rhodesiensis, an ancient ancestor of humans. The Universe has long experimented with what makes humans good survivors; today there are no homo rhodesiensis left. [Wikimedia Commons]

One might ponder what it is about humans that made us the fittest in our long line of ancestors? The Latin name for our species gives a clue to what we think the advantage is: homo sapiens means “wise man.” More often than not, our intelligence, our brains, are regarded as the prominent trait that made our survival most likely. The ability to make tools, to solve problems, and to plan for possible futures are all powers of the brain that suggest its development was a good survival trait.

But for those of us who think about life in the Cosmos, we eventually ask whether or not human intelligence is a survival trait or not? Look at the utter disregard our species has for the finite resources on our planet, or the fact that we are willfully ignoring the accelerating climate crisis, or any of a hundred other existential global threats we are ignoring. It makes one question whether our intelligence is being used for survival at all.

Interestingly, the brain is just like every other physiological trait we have — it was built by Nature through a long chain of experiments in survival. The earliest parts of the human brain to develop, the paleomammalian cortex (or limbic system), is the core of human emotion and response to external stimuli, particularly danger or threats. It evolved over time, like all of your biological systems, to protect you and give you a better chance at survival. One of its safety responses is to control your psychological response to threats. Sometimes that response is designed to protect you from very tangible direct harm; at other times it is designed to protect you from very tangible threats, but ones which may harm you by overwhelming your reactions until you are completely debilitated.

We see both of these deeply ingrained threat responses playing out right now in the ongoing crises that have ensnared the world.

Death has always preoccupied humans, in biological imperatives, deep psychology, and art. This 17th Century painting from Philippe de Champaigne is often associated with the Stoic philosophies surrounding Memento Mori: “remember that you will die.” [Wikimedia Commons]

Consider how we humans perceive and deal with death. A single death can transform your worldview — the death of a close friend or a loved one has profound impact on your mental state, precisely because of the deep personal relationship you shared. Death acutely focuses your attention on the fact the memories you carry with you will be the last ones you have with that person. It also acutely focuses your attention on your own mortality.

But you don’t have to be personally related to a person, or even know them, to feel grief at the loss of life. You feel the same pain, as if it were a friend or a loved one, precisely because you understand the deep personal loss from the death of a single person. Your brain has been wired from your personal experiences to understand how single people change one another’s lives. You extrapolate those experiences to people you don’t know when you hear of their death. The result is you are devastated, tortured by grief when they die. The deaths of famous people are a curious mix of the two, since you often ascribe deep personal evolution to your exposure to music, writing, sports, and film.

As a result, the loss of David Bowie knocks you down, because you remember driving in your car with friends listening to “Scary Monsters” over and over again, and those powerful memories are inextricably melded with your knowledge of Bowie. Chadwick Boseman’s death sent you into a paroxysm of tears, not just because you admired him in 42, but because your own family has been ravaged by cancer. Your rage at the murder of Breonna Taylor was stoked by the fact that she was murdered in her own home, a place of perceived safety and sanctuary.

Tragically, our brains behave in the exact opposite way when the scale of the tragedy expands beyond numbers easily related to your own personal experiences. Word of a family dying in a car crash or an apartment fire invokes a terrible sense of tragedy. News of an airliner going down may fuel your fear of flying, but large groups of people being overwhelmed by disaster becomes, for the most part, abstract to your brain. The reason is your brain is defending itself in a rather peculiar way. You absolutely can imagine the tragedy of the deaths of thousands of people — but multiplying the agony of grief for a single person a thousand-fold would destroy your psychological balance, and your brain knows that. It clings to the abstractness of large, anonymous numbers, and lets your thoughts gloss over the fine-scale human details of the tragedy. This effect is called psychological numbing.

Map of confirmed COVID-19 infections per capita (total divided by local population) as of 17 Sept 2020. The global scale of this crisis is beyond normal, everyday human experience. [Wikimedia Commons]

Which brings us to the current crisis. Without fail, the coronavirus Pandemic is a global crisis, not to be shirked and ignored. It kills people — 948,000 worldwide, and 202,000 in the United States (as of today, 17 September 2020). For virtually everyone who contracts the disease, there are long term consequences that we are only now beginning to understand — cardiovascular damage, fatigue, deterioration of your joints, and damage to your nervous system. The dire effects are why scientists and public health experts are so adamant about controlling the spread of the disease.

But unless you or a family member or a close friend have had (or died) from COVID-19, your brain protects itself. The psychological numbing associated with the scale of the pandemic takes over, and underpins all your thinking, regulating your personal behaviour as well as guiding your response to widespread social safety measures designed to cap the disease. Numbing can dull your sense of danger, leading to you not being as safe as you can be. An unfortunate lack of perceived danger might convince you that everyone who is responding with great caution are being silly, and it could lead you to rebel against social safety measures like a teenager against curfew. Your brain is protecting itself by convincing you it isn’t as serious as it is, but it is lying to you. You can control such responses, but only through diligent practice and self-reflection, and fearless trust in what the scientific data is really saying, not what we want it to say.

And so, our conversation returns to where it began. The brain of homo sapiens, with its capacity for abstract thinking and predictive speculation is the product of millions of years of evolution. Each stage in the long chain of natural selection helped our ancestors survive a ruthless and dangerous world, leading to us today.

So are our brains a trait that makes us fit for survival? The Universe developed our brains because along the way it seemed to be protective. But psychological numbing exposes us to threats that can decimate our species, like coronavirus to be sure, but other existential threats are on the horizon: pressures of population on limited natural resources, human wasting of natural environments, and the catastrophic collapse of the climate at the hands of humans. 

One could easily conclude that on the scale of our civilization, psychological numbing is not a survival trait, and the great experiment known as “humanity” will terminate, and fade into oblivion. It has happened before, with megalodons, sabre-tooth tigers, and trilobytes. That termination has happened to humans too — gone are our ancestors, Australopithecus, homo erectus, and the Neanderthals. But it has happened to our civilizations before too — gone are the ancient cultures of the Indus Valley civilization and Mesopotamia, and only fragments of the ancient Anasazi remain in the American Southwest, all erased by droughts that destroyed their supportive, agricultural systems. Humans are not immune to being erased by the Universe.

The Tree of Life is vast and tangled, but many more species have died than have lived, unable to survive the challenges the Universe throws at them. [Image: Pixbay]

But on the other hand the Universe has stirred another ability into the experiment — our capacity for reason, the ability to look at the Universe, figure out and predict what is happening and why, and doing something to protect ourselves. In some fashion, we have learned to utilize that trait and act in complete contraction to other biological imperatives our brain would like us to respond to. The Universe is testing out the idea that software updates, designed to circumvent hardware weaknesses and previous programming, might be a good survival trait.

Whether or not our reason adds to our survivability in the long term remains to be seen. We have yet to come to the end of this crisis, and do not yet know if our civilization can collectively shore up our defenses, or if we will continue to capitulate our future on the basis of wishful thinking. 

Either way, the Universe does not care. The Universe is callous, ruthless, unflinching. It is no mere tyrant, it simply has no reservations about terminating experiments that cannot survive in the face of adversity. Perhaps homo sapiens will sink into extinction; perhaps there will be some new strain of humans, homo postero, that will not be so fact resistant, and can survive more adversity than we.

As a brilliant fictional scientist once observed, “Life finds a way.” The Universe will find a strain of humans fit for survival, even if we are not.


This is the third in a series of posts about scientific reasoning, instigated by the Pandemic of 2020. The first post and links to the rest of the posts in this series are:

The Pea, the Cow, and the Giraffe

by Shane L. Larson

At a conference recently a colleague and I were having dinner, and talking about the woes of the world, a not altogether uncommon topic incentivized by some good wine and an excellent tutto mare.  As it turns out, my colleague is German, an excellent laser physicist, and was telling me about the German equivalent of a “silver bullet” cure for everything.  The German’s call this an eierlegende wollmilchsau, which translates into “egg laying wool milk pig” — an animal that provides everything!

Such a creature is, of course, non-existent, though some animals come close.  Cows are farmed for their meat, their milk, and the leather from their hides.  Chickens provide eggs and buffalo style chicken wings.  We don’t have a eierlegende wollmilchsau, but the contemplation of how we might get one begs a lovely question — where did all of the animals ennumerated in “Old MacDonald” come from?

Were all of the creatures seen on modern farms once wild and vicious?  Did there used to be vast herds of chickens covering the plains of North America?  Did black and white jersey cows used to scrape tooth and nail for survival in a world full of saber-tooth tigers and cave bears but now enjoy an idyllic farm life where humans provide them with food and water?  No, none of the creatures of the farm existed long ago in their present forms.  Almost all of them were created by us.

In the distant past, one of our ancestors decided that domestication of some animal species would be good.  The reasoning probably went on  the order of, “It’s hard work chasing this stupid water buffalo all over creation! When I finally kill it so we can eat it, I have to carry the stupid thing all the way back to camp which makes me even more tired!  If I trap him between all these trees we knocked over (let’s call that a “fence”; neat idea,huh?) and throw some grass in there for it to eat, I can kill it at my leisure some Saturday morning next fall before the snow flies, and we’ll have steaks all winter!”

After doing this for a couple of years, a friend in the cave next door said, “I’m tired of chasing and catching a water buffalo with you every year.  What if we catch a boy and a girl and have them make new baby buffaloes here each year? Then in the spring we can sit around and brew stump beer instead of chasing buffaloes.”  That was a good idea, so they built a bigger fence and started breeding buffaloes.

Once breeding started, the nascent farmers could be selective about how they bred their captive buffaloes.  They only bred animals that were large, to produce more meat, or they only bred animals with black hides because they liked the quality of the leather that resulted.  Over time, selective breeding strengthens the gene that produces each of these traits, and a new species, engineered by us, is born.  This process of selective breeding is known as artificial selection, and is responsible for all the domesticated plants and animals we know.  It is still widely practiced today, producing seedless oranges, high yield grains, and enormous Thanksgiving turkeys.

The genetic process of selection was first understood and described by Gregor Johann Mendel.  Mendel was an Austrian scientist and an Augustinian friar.  He came to understand how genetic traits are passed from parents to children through experiments with the hybridization of pea plants.  Between 1856 and 1863 he cultivated some 29,000 plants, carefully documenting hereditary traits and how they passed from one generation to the next.  His results were not immediately appreciated by the scientific community, and languished for nearly 40 years until they were “rediscovered” in the early 1900s.  Today, his work is the core of classical genetics, and explains the great success of sexual reproduction (reproduction with genetic exchange) as a strategy for maintaining genetic diversity.  Mendel’s Laws can be summarized as:

  • Every trait an organism has derives from heredity units, which Mendel called “factors” and modern biologists call “genes.” These factors are built from elemental pairs, with each element coming from one of the cell’s two parents.  Each factor is identified as being either dominant or recessive.  During the formation of sex cells, which are combined from each of the two parents, each sex cell only receives one of the elements from the pair the factors are built from.   Half the hereditary information comes from one parent’s sex cells, and the other half of the hereditary information comes from the other parent’s sex cells.  This is the Law of Segregation (Mendel’s First Law).
  • Every trait an organism has is passed on from parents to offspring independently of other traits.  If you are a cat with a brown-haired long tailed father and a white haired short tailed mother, your genetic adoption of a particular fur color is independent of your adoption of a tail length in your genetic makeup.  This is the Law of Independent Assortment (Mendel’s Second Law, or the “inheritance law”).

Mendel came to understand his laws of genetic inheritance by breeding peas and looking at flower colors of the offspring, either purple or white.  The flower color of pea plants, like many other traits in organisms, are inherited; they breed true from parent to offspring.  Mendel’s Laws explain the outcome of that breeding.  Consider eye color in humans.  The genetic expression of eye color is dominated by a signature for brown eyes, but recessively expressed by a signature for blue eyes.  Let’s call the element for brown eyes “B” (the dominant genetic expression) and the element for blue eyes “b” (the recessive genetic expression).  If a genetic pair has any element of the brown element B, then your eyes are brown — that is what we mean by “dominant.”  In order to have blue eyes, both your genetic elements must be the blue element b.

Mendel expressed this heredity in the context of a table containing two rows and two columns.  The headers for the columns are the genetic makeup of your mother, and the headers for the rows are the genetic makeup of your father.  The entries of the table then are all the possible mixtures of genetic information you receive from your parents together.

Let’s do an example of how this works.  I have brown eyes, and my wife has blue eyes.  My daughter also has blue eyes.  By what genetic pathway is that possible?  For my daughter to have blue eyes, she must receive a “b” factor from both of her parents, giving her bb genes.  Since my wife’s eyes are already blue, that means she automatically gives one of the “b” factors because her cells provided a bb starting point.  That means the other b factor came from me; but I have brown eyes!  That means I must have a recessive b trait, or my genetic makeup is Bb.  This is illustrated in the figure below (a Mendelian inheritance table).

A Mendelian inheritance table, showing how my daughter’s blue-eyed genetic makeup derived from the genetic factors carried by me and my wife, and passed to my daughter who has half of each of our genetic combinations.

As it turns out, that makes perfect sense.  My father has brown eyes, and my mother has blue eyes.  I must have picked up a “b” trait from my mother, and a “B” trait from my father.  But what is my father’s makeup? As it turns out, my brother has blue eyes, meaning he has bb genes, and so he must have picked up a b factor from my father, meaning my father also has a recessive blue gene for eye color.  AND SO ON…

There are six possible starting points: (1) Both parents have BB brown eyes. (2) Both parents have bb blue eyes. (3) One parent has BB brown eyes (dominant brown genes) and one parent has Bb brown eyes (dominant brown genes, with a recessive blue trait). (4) One parent has BB brown eyes, and one parent has bb blue eyes.  (5) Both parents have Bb brown eyes (dominant brown genes, with recessive blue traits). (6) One parent has Bb brown eyes, and one parent has bb blue eyes. The six possible tables are shown below.  Try to figure out what your family eye color heredity is!

The Mendelian inheritance tables, showing how a child’s eye color derives from each of the possible combinations of parental genetic makeup.

This discussion started with the domestication of animals.  An organism’s traits breed from their parental genetics, and the outcomes depend on the dominance of the genes.  We attempt to strengthen genetic expression when we domesticate animals by altering the statistics by which certain genetic factors are expressed.  Suppose my cattle population has two fur colors — dominant black fur (F) and recessive brown fur (f) — and I (erroneously) get it in my head that chocolate milk comes from brown cows.  I’d like to strengthen the occurrence of brown cows in my herd.  What do I do?  In a normal population of my cows, there are three genetic ways to have a black cow (FF, Ff and fF) and only one way to have a brown cow (ff).  If I want to increase the number of brown cows then I should breed brown boy cows (ff) with brown girl cows (ff) and the result will be brown baby cows (ff is the only outcome)!  The keys to artificial selection, are enforced selection of genetic traits, and time.

If I do this long enough, eventually I will encounter an anomaly.  I’ll get a white cow, or a tawny cow.  If the Cosmos really loves me, I’ll get a panda cow (these are called belted galloways, http://en.wikipedia.org/wiki/Belted_Galloway)!  What’s going on?  If I had all ff cows to start with, how did I end up with this completely new color?  The answer is genetic mutation.  Nature is a prolific author in the writing of genetic codes.  Most of what goes on in the nucleus of your cells is the transcription of genetic information — reading and copying the long sequence of codes that make up the genes that give you your traits.  Occasionally, errors are made, either because a random error is made or because an external event, like a cosmic ray or high energy photon, causes some damage, leading to an error. Genetic errors are like spelling errors; sometimes they produce complete nonsense, but sometimes they make something new that does make sense.  Consider the word firm.  A spontaneous letter mutation might change the i to a b, but fbrm spells complete nonsense!  But a spontaneous change of the i to a spells farm which does make sense!

Spontaneous mutations happen in genetics all the time.  When they don’t make sense, nothing happens.  Sometimes they do make sense, and something does happen — a kitten is born with stripes instead of spots; a baby duck has two green feathers instead of three.  As a farmer, I can choose to what to do about such mutations. I could choose to try and strengthen such mutations, or I could try to quell such mutations in my breeding stock.  Wheat that produces smaller yields is not planted in favor of wheat that produces double yields.  Radishes with bitter after tastes are not replanted and replaced with better tasting stock.  Apples that go rancid a week after picked are replaced by apples that store easily for a month or more.

What does Nature do with mutations?  Nature lets the mutations run rampant.  Suppose some 8 million years ago, you were a spotted ungulate (hoofed animal) living in the forests of what is today Africa.  You and your mate have lots of baby ungulates, and one day one of your progeny has a slightly longer neck than you.  What happens?  The slightly longer neck doesn’t seem to hurt the little tike, so life goes on.  She can reach higher branches than her siblings, so gets a few more of those ruffled fern leaves that you let the kids eat for a treat, but that seems to be the extent of it.  Some of her offspring have long necks too, and so this becomes a trait in the population.  Unbeknownst to you (the  ungulates haven’t developed science yet) the savannah around your forest home is expanding, and as it does the low-lying leafy plants that your kind feeds on becomes more scarce. Those ungulates which have shorter necks starve more often, and those with longer necks survive more often.  The surviving population is comprised of more long-necks, and so more of the baby ungulates are long-necks.  Pretty soon, there are a lot of long-necked ungulates around.  So many, in fact, that 8 million years later, they have a name.  We call them “giraffes.”

This process is called “natural selection,” and it is the natural counterpart of the “artificial selection” we discussed earlier. It is Nature’s way of farming, and it is responsible for all the diversity we see in the biological world.  The keys to natural selection, are random mutation of genetic traits, and time.

Will Nature ever produce an eierlegende wollmilchsau?  Probably not; there doesn’t seem to be any obvious reason why an egg laying wool milk pig will have a survival advantage over an ordinary pig.  But if you really wanted one, you could make one. By selecting the traits  you want, and breeding them true in your population of domesticated farm animals.