Nature and Nurture and Something Else (Plus Bees)

What makes you, you?  The nature vs. nurture debate has been going on for more than a century, and recent work with honeybees has managed to make it even more complex.  Researchers focused not on the nature part, the bees’ DNA, nor on the nurture part, how the bees grew up and lived, but on a fuzzy gray area in between.

All of the worker bees in a hive are sisters, descended from the same queen.  All of these bees grow up together sharing the same environment.  Worker bees divide into two groups: nurse bees, who take care of the eggs and larvae, and forager bees, who fly around collecting pollen and nectar.  Nurses’ and foragers’ missions are different, but the DNA of these sister bees is quite similar and their nurturing seems to have been the same.  How do they end up with different purposes?

Nurse bees working away

Enter epigenetics, a relatively new field that studies how the environment affects the expression of genes.  Genes were once thought to be instructions written in stone, unchangable directives for the cell.  The nurture effects were thought to go on after the instructions were read, a result of environmental factors, i.e. where a toxic chemical causes cancer or someone overcomes a natural stutter.  In reality, the genes themselves get buffeted by the winds of chance and circumstance from the outside world.  Epigenetics has found “tags” sitting on top of sections of DNA.  These tags control whether the cell will “read” a gene or if it will remain silent.  The DNA itself is not actually changed, but its accessibility is.  The whole set of DNA, called the genome, is overlaid with a pattern of these tags, called the epigenome.

This epigenome develops throughout life, starting with very few tags at birth.  Tags are added or removed due to environmental factors such as nutrition, stress, and disease, allowing cells access to some genes and not others.  Not only do these tags accumulate throughout one lifetime, some of them can be passed down to offspring.  Which means that parents, grandparents, and various distant relatives all gave some of their epigenome to an individual, contributing to how their genes are expressed.  They also contributed DNA, too, but unlike DNA, the epigenome is influenced by lifestyle choices.  Those grandparents’ actions and experiences, not just their genes, influence who you are.

Absolutly necessary dramatic cartoon.

After finding no difference between the genome and the epigenomes of the queen bee and workers right after birth, Dr. Andrew Feinberg and his colleagues at Johns Hopkins University examined the differences between the two castes of worker bees: nurses and foragers. These workers perform very different roles in the hive.  Usually, newly born bees start out as a nurses, and as older foragers die in the risky outdoors, some of them start foraging.  Researchers took care to compare the epigenomes of workers that were the same age, each nurse and forager getting the same amount of time to accumulate epigenetic tags.

In their experimental design, the researchers were sneaky. They took advantage of the ability of the workers’ ability to change jobs: switching back to nurse from forager if the need arises.  This doesn’t happen very often, but researchers created the need.  If we manipulate their hive a bit, and get some of the forager bees to change back to being nurses, they asked, what will their genome look like then?

While the forager bees were out foraging, the researchers moved the hives, so that the bees came back to another hive, empty of bees but not of honeycomb full of larvae that needed tending.  With a distinct need for nurse bees, half of the workers went back to their old jobs.  Researchers looked to see if foragers and nurses have different epigenomes, and what type of epigenome the foragers-turned-back-to-nurses had.

It turned out that not only did nurses and foragers have distinct epigenomes, but it seems the epigenome changed with the job.  When foraging worker bees were steered back to being nurses, their epigenome, and the genes it allowed to be expressed, reverted back to look like it did when it was a young nurse bee.  It was like flipping a switch attached to about 100 genes at the same time, turning them on or off if the worker was fulfilling a nurse role or a forager role.  These worker bees acted very differently, and the specific epigenome patterns seem to be the key to why.

Worker bee looking stylish.

This is, as the researchers note in very understated tones, “the first evidence in any organism of reversible epigenetic changes associated with behavior.”  Does our epigenome change our behavior or does our behavior change our epigenome?  No one knows, but this is evidence of the large role epigenetics plays in each individual.  And our epigenome is greatly affected by every facet of the environment we live in.  So how did you become you?  A murky causal soup of your environment, combined with your genes, combined with the gray area of environmentally-affected gene expression.  Epigenetics, and bees, have just made the nature-nurture debate much more interesting.


Calvin and Hobbes and Childhood Science

Imagination can be awfully addictive. I spent a lot of my childhood dreaming about made-up worlds, outer space and how the universe just doesn’t seem to make sense. I also ate up stories by other dreamers, from fantasy to science fiction. But there was one particular dreamer whose fantasies drew me in so long ago I can’t even remember when I got hooked.

Calvin and Hobbes was a story about an out-of-control dreamer. Not only that, but Calvin was a lover of the beauty of nature, so he tended to dream about the same things lovers of science dream about. Why is the universe the strange-seeming way it is? What happened millions of years ago? Is there intelligent life on other planets, and if so why haven’t we encountered it? All questions from a typical young mind trying to figure out the world.

I haven’t read the funny pages regularly since Calvin and Hobbes ended in 1995 — a wise decision by its creator, Bill Watterson, who didn’t want the strip to get stale. Fans of Calvin and Hobbes are also some of the most loyal, nostalgic comic fans out there. When the strip ended, it left a gap behind for a lot of us obsessive dreamers.

Now we live in an age of web comics. Many of these comics are far better than most of what you’ll find in newspapers today because these artists can lay their dreams and ideas out without worrying about the restrictions of syndication. Some of them wonderfully touch on the joys of science and explore the joy of childlike imagination much like Calvin and Hobbes did. But for me, Watterson’s strip will always be when I first saw science, beauty and imagination mix seamlessly.

The strip has been gone for longer than 15 years, but because its focus was on the timeless aspects of being human, Watterson’s humor and observations hold up today. Here’s a sampling of the most prominent science in Calvin and Hobbes:

Physics:  The duo decides to test special relativity by rolling down a hill in a wagon. Calvin famously renamed the Big Bang with the more sensationalist term “The Horrendous Space Kablooie” which even some cosmologists are fond of. Our protagonist even remarks on orbit trajectories as he flies off a swing.

Environmental and Planetary sciences: The strip had a heavy environmental message. A major setting was a vast plot of woods Calvin had access to and he hated to see it disrespected and damaged. At one point, Hobbes reminds Calvin that we need the Earth more than we need it. In one storyline, Calvin gets so frustrated with pollution that he and Hobbes go to Mars instead. This opened up a long storyline in which they have an encounter with the Viking spacecraft and even run into an alien. Calvin’s adventures visiting other worlds as the self-narrating Spaceman Spiff are also among his most dramatic and notorious.

Dinosaurs: But, for all his outer-space adventures, if Calvin was any kind of scientist, he’d probably be a paleontologist. He was obsessed with dinosaurs, and they were frequent guest stars in the comic. Oftentimes, Calvin imagined he was one. A lot of people who loved dinosaur science as a kid can probably identify with Calvin here. Though not everyone shared his wild imagination about the ancient reptiles.

Math: Contrary to his love of space and dinosaurs — and I’m guessing many biologists and my fellow writers will relate to this — Calvin struggled with math. He did everything he could to avoid it. Spaceman Spiff was not particularly helpful with Calvin’s math woes. Hobbes was full of smart-sounding but unhelpful advice. At one point Calvin, in my personal favorite of all the strips, even abused the abstract nature of mathematics to declare himself a math atheist.

Science Fiction: Calvin used his imagination to defy the laws of nature in a manner many kids do — with a simple cardboard box. That box became machines straight out of science fiction, using it for everything from shape-changing machine to a cloning machine to a time travel machine. Calvin predictably used his time travel machine to visit the dinosaurs, and narrowly escape being devoured by one.

Inquisitiveness: The 6-year-old protagonist didn’t spend the entire time in his head, though. He asked questions, and a lot of them. Calvin’s dad liked to play with his son’s curiosity, giving ridiculous answers to Calvin’s questions, such as what the wind is, what happens when the sun sets, and how load limits on bridges are determined. Calvin is largely remembered for testing his parents’ patience, but he tested a great many things. At Calvin’s best, he could be regarded a model for one of developmental psychologist Jean Piaget’s “little scientists,” intuitively testing and exploring how the world works.

What are some of your favorite strips?