Monthly Archives: May 2014

A Misleading Comic

I came across this comic the other day.

It addresses something very important: There are scientists and there are science enthusiasts. Science enthusiasts don’t always understand how science really works. Science makes great discoveries (it is the only thing that reliably can) but most people don’t know what this process really looks like. This is not in any way to demean those who are not scientists but who are interested in science. On the contrary, applaud those people and I hope more people get interested. My problem today is not the people who don’t fully understand science, but with the comic itself, which may have overshot its mark.

The first row of panels are spot-on. No problems there. I am regularly disappointed in the news coverage of scientific findings. Sometimes a news article will sensationalize the findings. Sometimes the importance or relevance of the findings will be wildly overstated. Sometimes the main point of the study will be missed entirely or they will get major facts completely wrong. People reading the news coverage may have no idea that there are problems. It is obviously best to read the primary source of the information, but (1) most scientific journal articles are behind paywalls, and (2) the point of science journalism should be that people don’t have to.

The second row of panels is where I start to have a problem.

Experiments don’t always work, and this causes a great deal of frustration for scientists. Failure is part of science. An experiment doesn’t work and you have to do it over again. You have to troubleshoot it with colleagues. Sometimes you have to put it on the back burner until you have the inspiration or technology to make the experiment work, and sometimes you give up on the experiment entirely.

But make no mistake — science DOES work, bitches. The comic appears to be arguing that, because individual experiments do not always work, it is incorrect to say that science works. This is my problem with it. There is a big difference between science as a whole and individual experiments. Science is the process through which we discover new information, and experiments are one of the major tools we use. While individual experiments sometimes turn out to be miserable failures, people in science believe in science. Otherwise they wouldn’t be in science.

In the third row of panels, the comic again seems to be conflating the outcome of an individual study with the whole process of science. It seems to be saying is that, because sometimes scientific results are confusing, the statement “science can answer any question” is false.

It actually gets a little bit confusing here because the statement “science can answer any question” is not entirely true. Opinions aside, there are likely to be empirical questions that science cannot answer. For example, Werner Heisenberg argued that it was not possible to simultaneously know the location and momentum of a subatomic particle. Without a time machine, it is probably not possible to know exactly what plant was growing at my location exactly 1000 years ago.

We don’t always know which questions are and are not answerable. The only way to truly tell if a question is answerable is to answer it. History is full of people believing that something was impossible, only to be proven wrong. James Baldwin once said, “Those saying it can’t be done are usually interrupted by others doing it.” A sharp contrast to Simon Newcomb, Professor of math and astronomy, who infamously said, (in 1906) “…no possible combination of known substances, known form of machinery and known forms of force, can be united in a practical machine by which man shall fly long distances through the air…” Regardless of whether we think an empirical question is possible to answer, science is our only chance at finding an answer. As scientists, we always have to believe that it is possible to discover the answer to any question.

Have a topic you want me to cover in a future post? Let me know in the comments or on twitter @CGEppig.

Advertisements

The Tragedy of the Commons

In my recent post on greed, I explained how the underlying psychology that leads some people to have an intense and selfish desire to acquire wealth evolved. In doing so, I focused on how these traits favored individuals that had them in the past. One reader pointed out that this leads to resource depletion in humans (which it does), and wanted to know whether this or any other “bad outcomes” occur in other species.

The drive to leave more surviving offspring than other individuals is integral to the evolution of all traits. Reproduction is the only currency of natural selection, and all traits are tied back to this in one way or another. Survival is an important trait, but it is only important so far as living longer allows one to leave more offspring. Social behavior is important for some species, but only if it improves survival and reproduction. The same goes for intelligence, opposable thumbs, wings, or any other trait.

It’s obvious to see how the drive for reproduction can be bad for other species. For example, if an animal enhances its survival and reproduction by being a predator, the survival and reproduction of its prey will suffer — being eaten for lunch certainly qualifies as a “bad outcome.” For this post, though, I’ll focus only on how the evolutionary ambitions of a species can hurt itself.

Parasites have the same drive to reproduce that other organisms have, although the drive is based entirely on physiology instead of having a psychological component. Their lifestyle requires them to be careful (in physiological and evolutionary terms) about how fast they consume their resources (their hosts). If they reproduce too fast inside their hosts, the host will become so sick that it cannot transmit the infection effectively anymore. The virulence (pathogenicity) of a parasite is carefully tuned to suit the host. If a parasite jumps to a new host species, the virulence may be too high to be good for the parasite. This is exactly what happens with ebola.

The ebola virus sometimes infects humans, but we are not its primary host. In humans, ebola is very contagious but it kills the host very quickly — too quickly to infect enough other hosts. For this reason, ebola outbreaks in humans tend to “burn out” fairly quickly and do not infect large portions of our population. Humans are the virus’s resources, and by reproducing so quickly, the resources are depleted and the virus population dies out.

Electron micrograph of an ebola virion. Image from wikipedia.org

In the boreal forests of North America, the Canadian lynx (Lynx canadensis) has a 9- to 11-year cycle of population increase and decrease. The Canadian lynx specializes in hunting the snowshoe hare, and they are very good at it. Lynxes that are better at catching snowshoe hare will get more resources, and are able to have more offspring. These offspring will inherit a superior ability at catching snowshoe hares, allowing them to have more offspring of their own. Hares are renowned for their rapid reproduction, but the lynx is renowned for its ability to kill hares. When the lynx population gets too big, they will kill so many of the hares that there is not enough food left to support the lynx population. The lynxes starve to death and the population crashes.

 

Canadian Lynx (Lynx canadensis). Image from wikipedia.org

This is obviously not a complete list of how resource consumption can result in problems for non-human species, but it shows that it can be a real problem. Most resources are limited, and the tragedy of the commons applies to everyone, human or not.

 

 

Have a topic you want me to cover in a future post? Let me know in the comments or on twitter @CGEppig.


What Causes Greed?

This week’s topic was requested by a reader. If you would like to request a topic, let me know in the comments or on twitter.

Before we begin, be sure to read my post on the naturalistic fallacy. Science cannot condemn or justify any behavior — it can only identify the behavior and explain why it exists. In this post I will attempt to explain greed as I understand it, without mixing in any of my own ideology or the ideology of anyone else.

My dictionary defines greed thusly: “Intense and selfish desire for something, especially wealth, power, or food.” It is the wealth part that I will focus on.

To understand greed, or many other human behaviors, we first have to understand evolution — the human mind, of course, is a product of evolution. Every behavior and thought that we have is not necessarily the direct result of natural selection, but natural selection lays the foundation for our behavior. Natural selection works on a relative level. Traits are successful if they are passed on more frequently than other traits, which means that more individuals with that trait must be born and survive than individuals with other traits. Traits will evolve faster if there is a greater “selective advantage” — that is, the difference in survival and reproduction between individuals with and without the trait is very large.

If a squirrel, for example, has three offspring that survive, it and its traits are doing better than a squirrel that only has one offspring that survives. But it is not doing as well as a squirrel that has 10 surviving offspring. For this reason, natural selection does not give animals a target number of offspring that they want to have over the course of their lives but not exceed. If a squirrel has 10 surviving offspring but could produce more, it will lose the evolutionary race to an individual that could produce more than 10 surviving offspring and does. Said differently, natural selection does not produce squirrels that are satisfied with a particular number of offspring and will not have more. Rather, natural selection produces squirrels that will produce as many surviving offspring as they can. This is true for all organisms, not just squirrels.

For all organisms, resources are the most important thing for reproduction. It takes a lot of calories to produce an offspring, and raising it (in species that provide parental care) takes even more. Animals will produce as many offspring as they can, and it is resources that determine how many this really is. There is a large selective advantage for individuals who can acquire the most resources because they can produce more offspring that are healthy and survive long enough to reproduce themselves.

Modern humans aren’t so different. Estimates vary, but it costs somewhere in the area of $100,000 – $200,000 to raise a child to age 18 these days. This means that you need to have at least this amount of money coming in for every child that you want to have.

But let’s go back in time for a minute. Back in the day, let’s say 50,000 years ago, there was no money. If someone got a windfall of resources by killing a mammoth, they couldn’t put it in the bank, or even horde it underneath their mattress. If they did not use this material wealth, it would rot.

Modern wealth is easily storable, so it can be accumulated in ways that was not possible in the past. Prehistoric people could not stuff an uneaten mammoth under their mattress for later, but modern people can easily stuff the equivalent of a thousand or a million mammoths into a bank account or a mutual fund and keep it for as long as they want.

As animals, we have a strong drive to do better than everyone by as much as possible. Humans obviously have complexities to our behavior that make us more nuanced, but this drive is still rattling around in our brains and affecting our behavior. Just like the squirrel that tries to have more surviving offspring than the other squirrels, people like to have more wealth than others. Natural selection has made us very interested in acquiring more resources than other people.

There is an old joke about a farmer who is granted a wish, but whatever he wishes for will be doubled for his neighbor. He can’t wish for a wealth of gold because his neighbor will be given double the gold. He can’t wish for five strong sons because his neighbor will get ten strong sons. He eventually decides to wish for half of his crops to be destroyed. This solution, or one like it, is the only way he can come out ahead of his neighbor. Coming out ahead, as I have already discussed, is the only way to win at natural selection.

Nobody particularly needs a billion dollars, but lots of people want it. When natural selection built us with an interest in accumulating more wealth than other people (what you might call an intense, selfish desire for it), it did not build an off switch.

And that, in a nutshell, is why we have what we call greed.

See the followup to this post: The Tragedy of the Commons

Have a topic that you want me to cover? Let me know in the comments section.

Follow me on twitter @CGEppig


Do Genes Skip Generations?

Do Genes Skip Generations?.


Do Genes Skip Generations?

I often hear casual mention of this or that gene “skipping generations.” Is this really possible? Can genes skip generations? As posed, the answer to this question is “no.” Genes do not disappear and then reappear in later generations. But the expression or manifestation of genes — traits — can skip generations under some circumstances.

First, a quick lesson on genetics. If you already have a passing familiarity with how inheritance works, you may want to just skim the next bit. Genes, or “loci,” (singular: locus) are regions of DNA, but not the DNA sequence at the region. (The word “gene” is sometimes used to mean other things, but this is the definition I’ll be using for this discussion.) The actual sequence of DNA at the locus is called an “allele.” A gene or locus is where the DNA is found that produces a particular trait, and the allele at the locus determines the nature of the trait. For example, there are genes that control finger length. You might have an allele at that locus that gives you long fingers or an allele that gives you short fingers. At a locus that controls eye color you could have an allele that gives you blue eyes or an allele that gives you green eyes. (Eye color is actually controlled by many different genes, but I hope this gives you the idea.)

Typical humans have two copies of each chromosome, and therefore have two copies of each gene. The alleles at these loci may be two identical copies, or two different versions. When you have two different alleles for the same trait, they have to decide which one gets expressed. Some alleles are dominant and some alleles are recessive. If a dominant allele is present, then the trait that the allele codes for will be expressed, regardless of what the other one is. If a recessive allele is present, it will not be expressed if there is also a dominant allele present. For a recessive trait to be expressed, there need to be two copies of it. Take our earlobes, for example. The dominant allele produces free earlobes, and the recessive allele produces attached earlobes (see picture below). If you have two dominant alleles, you will have free earlobes. If you have one dominant and one recessive allele, you will also have free earlobes, because the presence of just one dominant allele will always result in the expression of that trait. If you have two recessive alleles, you will have attached earlobes.

A free earlobe is shown on the left and an attached earlobe is shown on the right. Image from opencurriculum.org

A free earlobe is shown on the left and an attached earlobe is shown on the right. Image from opencurriculum.org

This is true for all genes except those that are located on the sex chromosomes. The X and Y chromosomes have different genes on them. Human females, who have two X chromosomes, have two copies of each gene on the X chromosome. Human males, who have one X and one Y, have only one copy of all of the genes on the X chromosome, and one copy of all of the genes on the Y chromosome. When there is a recessive allele on a chromosome that there is not a second version of (i.e. the X and Y chromosomes in males), it will be expressed even though there is only one copy of it, because there is no other allele to be dominant over it.

For people with two X chromosomes, one is inherited from each of her parents. Her mother, who has two X chromosomes herself, gives one of her two X’s at random. From her father, she will inherit the only X chromosome he has. For people with one X and one Y, the X always comes from the mother (who only has X’s to give) and the Y always comes from the father. This has some very particular implications for inheritance.

If a man has a particular allele that is located on the Y chromosome (a “Y-linked” trait), he will pass it on to his sons 100% of the time, because sons always get their Y chromosome from their father. If he has a particular trait that is located on the X chromosome, he will never pass it on to his sons. He will have a 100% chance of passing the allele on to his daughters, and they will express it or not based on the normal rules of allele dominance.

If a woman has a particular trait that is located on one of her X chromosomes (an “X-linked” trait), there is a 50% chance that it will be passed on to either a son or a daughter. If the son inherits the trait, he will always express it, because he only has one X chromosome. If a daughter inherits the trait, she will express it or not based on the normal rules of allele dominance.

Here is where the generation skipping comes in. Consider this family:

Our first generation people are Bob and Sue. Bob has a recessive allele on his X chromosome, shown in blue, and Sue does not. Because Bob only has one X chromosome, this recessive allele is expressed. When they have children, their son, Fred, will inherit an X chromosome only from his mother, so he does not inherit his father’s recessive allele. Their daughter, Jill, inherits one X from her father, which carries the recessive allele, and one X from her mother that does not have the allele. Jill will not express this trait because it is recessive.

Family tree 1

Fred marries Jean, who does not carry the recessive allele. None of their children will inherit the recessive allele because neither of their parents had it.

Family tree 2

Jill marries Kyle, who does not have the recessive allele. Half of their sons will inherit the recessive allele and express the trait. Half of their daughters will inherit the allele but will not express it.

Family tree 3

So who in this family expresses the recessive allele? Only Bob and one half of Jill and Kyle’s sons. The trait skipped Fred and Jill’s generation, although Jill carried an allele for it.

Recessive x-linked traits include red-green colorblindness, hemophilia and adrenoleukodystrophy.

I have written further on this topic here.

Have a topic that you want me to cover? Let me know in the comments section.

Follow me on twitter @CGEppig