Sunday, September 26, 2021

Greetings from Thumbelina


Some time ago, I posted a Darwin video about Thumbelina. This is a very old story, continually reappearing in new children’s books, about a young woman who is so small that she can hitch a ride on the back of a swallow or hide inside of a tulip (to use the two examples from our public library). We all know it is impossible to have a human being this small, but why is this so? 

Organisms can be very small. If you define an organism as something that can actively maintain constant internal conditions, and can reproduce itself, then the smallest organisms on Earth are bacteria and archaea. Viruses are smaller, but they cannot maintain constant internal conditions, or reproduce, by themselves; they have to outsource these processes to the cells that they parasitize. Astrobiologists (scientists who generate fact-based speculations about possible life on other planets) have lively disagreements about what the smallest life forms could be.

How small could a vertebrate be? A vertebrate is an animal that has (in addition to vertebrae) whole systems of organs that maintain constant internal conditions. Vertebrates are so complex that they could not possibly be microscopic.

But they can be pretty small. Scientists recently discovered a frog, Paedophryne amaneusis, that is so small that it can comfortably sit on a dime. X-rays reveal that it has a complete skeleton. It does not have a tadpole stage, but it attracts mates with ultrasonic peeps. I suspect that it does not need to have as much anatomical complexity to maintain internal conditions; for example, it probably absorbs most of the oxygen that it needs through its skin.

This image is from the source in this link.

Humans have seventy trillion cells. Would Thumbelina need to have seventy trillion very tiny cells? Probably not. She could have tiny organs that did everything that they needed to do, each organ with fewer and smaller cells.

But there is one organ that would need to have a minimum size: the brain. While Thumbelina could metabolize as she rode around on the back of a swallow, she would not be able to enjoy it, or even know what was happening. Since no one knows how to define consciousness, we cannot say how big a brain has to be to be conscious; but Thumbelina’s brain would definitely be too small.

Probably everyone has heard about the homunculus. This is supposedly a tiny complete person that lives inside of a sperm head, made famous by the Nicolaas Hartsoecker drawing (1695). According to many scientists of the late seventeenth century, that is where people came from: a little person inside a sperm grows up by consuming the food inside the egg. Some of the sperm had little men, some had little women, as in the drawing. Even more amazing, the male homunculi had sperm, with homunculi inside of them, with homunculi inside of them, with…how far can you go? Forever? Scientists at the time knew no reason to doubt it.

The reason that you cannot have an infinite regression of smaller and smaller objects is that everything is made of atoms. Although atoms are incredibly small, they are not infinitely small. This places a lower limit on the size of anything made out of atoms.

We must be careful to avoid the argument from incredulity: If I cannot believe it, then it cannot exist. Not long after I post this essay, a computer scientist might create a qubit structure that could fit inside Thumbelina’s head and impart a reasonable level of intelligence. But the principle remains unchanged: there is a lower limit of brain size for human intelligence, and Thumbelina is probably below that limit.

There are upper limits also. A very large walking vertebrate could not exist, since volume (weight) increases as the cube of the linear dimension while the strength of a leg increases only as the cross-sectional area (the square). An animal twice as big in linear dimensions would have legs four times as strong but would weigh eight times as much. This is true only for animals that walk on land. Whales can be much larger, but their weight is supported by the buoyant force of the water that they displace.

None of this will make any difference to people who are enjoying the new King Kong vs. Godzilla movie, or to my granddaughter who enjoys the Thumbelina books. But, I suspect, human imagination is limited—not by size, but by our evolutionary heritage. We imagine things that our evolved brains allow us to imagine, and nothing more.


Thursday, September 16, 2021

Has the Pandemic Made Us Appreciate Science?



One would think that the pandemic would have made Americans want to learn more about disease and health, about how to minimize the spread of disease by means of vaccination, social distancing, etc. In fact, this is what science writer Robin Marantz Henig said in the November 2020 issue of National Geographic: “Maybe the pandemic will persuade even the skeptics how crucial scientific discovery is to human flourishing.”

At the time Henig wrote this, it seemed so inescapably reasonable. But this has turned out to not be the case. The surge in covid cases in America, the great majority of them among the unvaccinated, has only strengthened the anti-science fervor among many Americans. About half of Americans disregard science, and many of these openly detest it. Rather than acknowledging that masks slow down the spread of covid, some states not only do not have mask mandates but have made these mandates illegal. Here in Oklahoma, it is illegal for schools and other state entities to require measures that protect either children or adults. It is difficult to appreciate the depth and scope of the hatred that many Americans feel toward science, whether it is the study of how diseases spread (epidemiology), or any other branch of science.

Right now, as shown in this graph from a French news website, America is leading the world in the number of covid deaths per day. Brazil used to be the leader, and Indonesia was briefly, but America has gone back to being the world leader in covid deaths per day.

As a science educator in rural Oklahoma, I feel quite despondent right now about the hostility of my neighbors toward any kind of scientific evidence about anything. I used to be inspired in my work; now, I just count the days to retirement.

Friday, September 3, 2021

Why Hasn't China Gone Green?


A special Labor Day essay!

China is the world’s biggest investor in and producer of green energy. Their participation in solar and wind energy is nothing short of breathtaking. They would seem to be a model to the rest of us of how an economy can go green.

They are, however, also the world’s biggest investor in and producer of dirty energy, in particular coal. In addition, they notoriously pollute the environments of their own billions of expendable citizens.

They are the best and the worst. What is going on here? May I speculate?

First, they know that green energy is the unavoidable path of the future. Civilization will collapse into a dark ages pile of wiggling failures if we do not embrace renewable, clean energy. They know this as much as anybody. They do not deny it, unlike the executives of American coal and oil corporations. Accordingly, China (led by its top-down imposition of economic priorities) leads the world in technological innovation of green energy. Someday, they are poised to lead the world.

Second, they also desire to bury the United States. I do not mean in a nuclear or violent way. But they want to bury us as a serious economic competitor. They plan to do this by out-producing us. They appear to be successful. They sell much much more to us than we sell to them. They will do this by using clean energy or dirty energy, whatever is at hand. Once they have buried us, they will be glad to switch to green energy, and at long last let their gasping, sick citizens breathe freely and let the skies become clear.

They are walking a tightrope, but they have done so many times before. They appear confident that they will lead the post-American world into a green energy future.