Book: Your Inner Fish

Sonic hedgehog

Teeth are the great equalizer.

Neil Shubin wrote:

Let's take a hypothetical humorless, quite unclown-like couple who have children. One of their sons was born with a genetic mutation that gave him a red rubber nose that squeaks. The son grows up and marries a lucky woman. He passes his mutated nose gene to his children, and they all have his red rubber nose that squeaks. Now, suppose one of his offspring gets a mutation that causes him to have huge floppy feet. When this mutation passes to the next generation, all of his children are like him: they have a red rubber nose that squeaks and huge floppy feet. Go one generation further. Imagine that one of thee kids, the original couple's great grandchild, has another mutation: orange curly hair. When this mutation passes to the next generation, all his children will have orange curly hair, a red rubber nose that squeaks, and giant floppy feet. You may ask, "Who is this bozo?"

Of course this argument is nonsense. Everyone knows clown genes are recessive -- otherwise we'd be overrun with clowns.

WE ARE!

Point Howard.

Neil Shubin has a new book (2020) called "Some Assembly Required" about how DNA repurposes structures for new abilities, leading to the evolution of new species.  It very much fits into the Evo-Devo  world of Sean B. Carroll, which explains much of the inexplicable history of life.

Enjoying this one a great deal.

Our DNA strings are enormous, 3.2 billion pairs.  Each strand would be six feet long if uncoiled. Your body has 4 trillion cells.  If those 4 trillion DNA strands were laid end-to-end, they'd reach almost to Pluto.

Scientists used to think most of it was "junk DNA."  Only 2% of our DNA encodes for structures, the other 98% was considered useless or anachronistic, inherited from older antecedents and never weeded out.

Scientists know better now.  Every cell in your body has exactly the same DNA, and it's the non-coding DNA that determines whether the cell is a blood cell, a muscle cell, or a bone cell because of the timing in the protein expression. There are 200 different kinds of cells, all built from identical DNA.

 "Junk" DNA also controls fetal development, so mutations there can cause you to have four arms instead of two or six fingers instead of five (see "Hemingway's cats").  Mutations to non-coding DNA can cause all sorts of weird birth defects, most fatal, but not all.

Mutants that are viable can pass along their mutated DNA -- thus allowing a pathway for instant changes that aren't developed through the long process of descent with modification and survival of the fittest.  Mutations especially in the DNA that controls fetal development can lead to speciation, if the gene is dominant or the mutation is beneficial.

Enjoyed "Some Assembly Required" so much that I bought Neil's only other book, "The Universe Within" which came between the two.  It's not as good, though certainly finishable.

Not all the speculations contained therein are supportable.  It's mainly about how all the heavy elements that make up our world are byproducts of supernovas and exploding stars, so our solar system had to wait a substantial percentage of the age of the universe (67%) to form. Life formed about a billion years (another 7%) after that.  That part makes sense, but other parts don't.

Some of my quibbles are minor.  Shubin says the seven-day week comes from scripture, but it's actually almost four millennia older than that.  He correctly ascribes the 60-minute hour to the Babylonians, but doesn't mention the 24-hour day.

ABC Science wrote:

Our 24-hour day comes from the ancient Egyptians [c. 4000 BCE] who divided day-time into 10 hours they measured with devices such as sundials, and added a twilight hour at the beginning and another one at the end of the day-time, says Lomb.

"Night-time was divided in 12 hours, based on the observations of stars. The Egyptians had a system of 36 star groups called 'decans' — chosen so that on any night one decan rose 40 minutes after the previous one. In the Egyptian system, the length of the day-time and night-time hours were unequal and varied with the seasons. In summer, day-time hours were longer than night-time hours while in winter the hour lengths were the other around," says Lomb. [Although, being nearer the equator, the differences were only about 4 hours from the summer solstice to the winter solstice.]

The subdivision of hours and minutes into 60 comes from the ancient Babylonians [c. 2000 BCE]  who had a predilection for using numbers to the base 60. We have retained from the Babylonians not only hours and minutes divided into 60, but also their division of a circle into 360 parts or degrees," says Lomb.

"What we have not retained is their division of a day into 360 parts called 'ush' that each equalled four of minutes in our time system." Lomb says it's likely that the Babylonians were interested in 360 because that was their estimate for the number of days in a year. Their adoption of a base 60 system was probably allowed them to make complex calculations using fractions.

https://www.abc.net.au/science/articles/2011/11/15/3364432.htm

He mentions that the color bands in 400-million year old coral deposits indicate that there were 400 days in a year back then, instead of 365, so the Earth's rotation is slowing down. He doesn't do the math that follows that discovery though.  If the Earth's rotation is slowing 2.5% per hundred million years, that means the Earth spun about 11.5% faster when it was formed (if my maths is right...). How would that affect gravity at the surface?  Was the circumference of the Earth very much smaller then?  He doesn't say... but the maths should be possible.