What makes each human seem unique?

Sunday January 6, 2013

Q: Let’s celebrate the uniquenesses that help make each of us into a One-and-Only YOU. Can you name a few?

A: Most basic is the human genome containing some 3.2 billion letters of the DNA code, with about 16 million of them accounting for all of our individual differences, says Caroline Williams of "New Scientist" magazine.

Since the code has four letters, the number of possible combinations is four raised to the power of 16 million, "more than enough to go around everybody who has ever lived, many times over. So the chances of anyone having exactly the same genome as you is zero, true even for identical twins."

Though fingerprints are determined largely by genes, those of a developing fetus are tweaked by subtle pressures from the womb walls and amniotic fluid, helping make even identical twin prints unique.

Analyzing faces, our most obvious badge of identity, one recent Norwegian study found that 92 percent of them had at least one lookalike that neither human observers nor facial recognition software could tell apart ("Lecture Notes on Computer Science").

Still, faces are pretty good markers, as is gait. Since our ancestors first stood upright 1.5 million years ago, humans have all generally walked the same way. But studies going back to the 1970s have shown that we’re able to recognize people we know from their walk alone at least 90 percent of the time.

Scents too are largely unique. Dogs have always known this, and now science can prove it. One analysis pointed to a mix of 5,000 acids, alcohols, ketones and aldehydes -- 44 of them different enough to form an individual chemical profile like a fingerprint ("Journal of the Royal Society Interface").

And though singers croon of two hearts beating as one, recordings of electrical impulses show that "in reality, no two heartbeats are the same." Also, because heartbeats are subconsciously controlled, they are almost impossible to fake, opening the way to experimentation with ID cards and "heartbeat passwords" to protect private information.

Q: Given the sequence B-D-G-K-P, can you say which letter comes next? Hint: There are two very different ways of solving this "brain trainer."

A: Approach No. 1 works with letters: Starting with the B, just insert C to get to D; then E and F to get to G; next H, I and J to get to K; and L, M, N and O to get to P. Since you inserted one, then two, then three, and finally four letters, the next insertion should be five letters, or Q, R, S, T and U to get to V -- which is the solution to the puzzle.

Approach No, 2 converts all letters into their corresponding numbers: A=1, B=2, C=3 and so forth. This turns the B-D-G-K-P sequence into 2, 4, 7, 11, 16. These numbers increase by 2, 3, 4 and 5 respectively, so the next number is 16 + 6 = 22, which corresponds to the letter V, the puzzle’s solution (from "Science Illustrated" magazine).

Q: How is it that a high-jumper can both clear the bar and fail to pass over it on the same jump?

A: "Surprisingly, it is possible for the high jumper’s body to fly over the bar while his or her center of gravity passes below it," says Rose Eveleth in "Scientific American" magazine. Called a "Fosbury Flop," the technique is named after Dick Fosbury of the U.S., who first executed it at the 1968 Olympics and went on to win the gold medal, adds John D. Barrow in "Mathletics: A Scientist Explains 100 Amazing Things About the World of Sports."

Here, the high-jumper’s curved body passes clearly over the bar while his "theoretical" center of gravity passes as far beneath the bar as possible, making optimal use of his or her "explosive takeoff energy."

"Now, you might ask, why do many of today’s jumpers use this backward leap," poses Eveleth. That’s easy: "When your back is to the pole, there is less chance that your arms or legs will hit the bar and knock it down."

Send STRANGE questions to brothers Bill and Rich at strangetrue@cs.com.


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