Prime Numbered Cicadas

2013 Brood II cicadaRight now, the northeastern US is experiencing a plague of cicadas. These are no ordinary cicadas, however – these are “Brood II” of the famous 17-year periodical cicadas (a collection of species under the genus Magicicada). There are 15 distinct living broods, which can also have 13-year periods as well as 17. Brood II is far from the most wide-spread: for 17-year broods that goes to X, while for the 13s it’s XIX.*

Noting this, Brian Thomas writes Cicadas Make Great Mathematicians. Really now?

Entomologists study insects and spiders. They regularly discover examples of mathematical genius hardwired into various tiny-brained arthropods. And as young students know all too well, math doesn’t come easy.

As he has done before, Thomas confuses mathematics that must be learnt directly, like times tables, with that which is more innate, like throwing a ball. You could describe throwing and catching as the solving of complex differential equations, but that entirely misses how these processes actually happen. In this case, the ability of some cicadas to emerge at 13- or 17- year intervals does not require that they, or anyone else, actually know how to count.

Science writer Seth Borenstein recently wrote an AP article describing why residents of the United States’ east coast anticipate an impending insect invasion—at least in rural areas. This spring marks 17 years since a particular brood of a unique kind of red-eyed cicada, called “magicicada,” last emerged en masse. And yes, the name reflects the way these insects seem to “magically” appear at the same time after 17 years of living underground as larvae. When the ground temperature reaches precisely 64 degrees, magicicadas in “Brood II” will tunnel upward, crawl up the side of a nearby tree or structure, squeeze out of their molted exoskeletons and then fly around each [sic] in search of a mate.

That article can be found here (Thomas’ own link appears to be broken). I can’t actually find where the Magicicada name comes from, though Thomas seems to be confident that the obvious “magic” root is the correct origin.

When Brood II emerges together, some estimate they will number up to a trillion cicadas. Of course, their onboard precision-computing equipment makes this all possible. Some kind of internal miniscule chronometer precisely measures the passage of years, and a tiny thermometer monitors the soil temperature. These nifty devices would be useless unless they had the ability to communicate—according to appropriately engineered software—with a central processor. Only then can the organism attach meaning to the data input, and act accordingly.

Human inventors have built machines that include thermometers, central processors, and the means for them to send, receive and interpret temperature data. But such inventions will probably never achieve the scale of miniaturization found in tiny insect bodies. No wonder University of Illinois entomologist May Berenbaum told AP, “It’s just an amazing accomplishment. How can anyone not be impressed?” Similarly, Mike Raupp, an entomologist at the University of Maryland said, “These guys are geniuses with little tiny brains.”

These quotes are all from the AP article. There isn’t a lot of context for the quotes even in their original articles, which is a pity.

So, even secular scientists recognize the genius inside insect’s instincts. But unfortunately, they mistake the origin of that genius. Raupp told AP, “These guys have evolved several mathematically clever tricks.” They should know better.

In all the versions of the AP article that I can find the explanation of what these “tricks” are is omitted. Biological rhythms, like the ~24-hour circadian rhythm, aren’t terribly difficult to set up or modify. In this instance we likely have a factor that simply slows the normal development of a cicada by enough to make it emerge 13 or 17 years rather than shorter periods. The synchronisation – all the cicadas in a given area usually appear at once – is probably due to those appearing in less-population dense years being more likely to be eaten at once. While the period seems to be genetically determined the fact that some “stragglers” appear in the wrong year, only to be quickly eaten, is evidence that it can be modified and thus evolved. If we take Thomas’ approach, however, it is evidence that God can’t count.

Here’s an interesting claim:

After all, their own secular textbooks teach that one way to recognize a clear signal from extraterrestrial life is to track the prime numbers it might broadcast if it were an intelligent programmer. Magicicada broods spend either 17 or 13 years living underground, and both are prime numbers. If a series of prime numbers came from outer space, secular astronomers would have no doubt that an intelligence sent them. But apparently their inference-making skills lapse when prime numbers occur in creatures right at their feet!

The textbook chapter to which Thomas refers can be found here. The particular example being talked about there involves the transmission of a collection of binary 1 and 0 signals that was the length of two prime numbers multiplied together. If arranged into a rectangle – the use of prime numbers to determine length limits the ways you can do this to only two – one of the possible arrangements would reveal a picture. The point is that this is a way to transmit complex information without it being too difficult to guess, at the other end, how to decode it.

Another, very different method that only lets you transmit the signal “We are here!” is to transmit a series of prime numbers, or perhaps the digits of π. If we detected a signal containing the digits of π we could reasonably assume that it came from an intelligent source. However, if we saw a ring of ripples in water and observed that the ratio between the lengths of the circumference and the diameter was exactly the value π we could not make that assumption. The difference is that the π-signal is arbitrary and unlikely without the influence of intelligence – it seems unlikely that any natural process could create a listing of the digits, but intelligent life can reasonably be expected to know them to be special- while the π ratio is an inherent property of circular ripples.

Back to the prime numbers, and the cicadas: if a signal of the length 221 (17 multiplied by 13) was detected, that would be reason for interest, and if it revealed a meaningful pattern then we could assume intelligence.** The difference between this and the cicadas is that, in the latter case, the choice of numbers are not arbitrary. Prime-numbered periods – particularly, in the 10-20 range, 13 and 17 – are inherently advantageous, and so are more likely to exist. Therefore we do not require intelligence to explain why there are no 15-year cicadas, given that natural selection can operate here and will lead to the result observed.

Thomas concludes:

Having to attribute these insect’s “amazing accomplishments” to mere natural processes must frustrate otherwise extremely smart secular scientists. Satisfaction, not frustration, awaits those who ascribe genius insect math to a real live Mathematician. “For by him were all things created, that are in heaven, and that are in earth” (Colossians 1:16.)

“Mere natural processes”? Thomas does not seem to have much appreciation for the world around him (and does he really think that God does it directly?). Perhaps he would have benefited if we could have heard more of what Dr Raupp had to say.

*The reason why one is called XIX (19) when there are only 15 total (plus two extinct broods) is that there are 30 (13 + 17) possible broods and they are numbered accordingly even though some don’t actually exist.

**Personally, I have my doubts about the likelihood that this system would ever be considered by another species, but you never know.

I’m still investigating the dinosaur skin story from Monday – I’ll post that tomorrow, hopefully.


3 thoughts on “Prime Numbered Cicadas

  1. SGU discussed the cicades. Theire explanation for the prime number thing is that it means the emergences of the various broods will never coincide, so they can’t be wiped out by a single bad year (or predators learning to predict it etc.)

  2. Reading about the synchronization of the emergences and the stragglers reminds me of how pendulums can “naturally” synchronize (Huygen’s Odd Sympathy ).

    It also reminded me of how fertile adult women will synchronize their menstrual cycles if they live together. I don’t think magicicadas are communicating with each other through pheramones, but it happens to the women involuntarily. They certainly aren’t doing the math, which is what BT is insinuating.

    Here in Arizona we have the plain ol’ annual kind of Cicadas. I like them, despite their hideous appearance, because their [insanely loud] buzzing sound is the soundtrack of summer.


Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s