First of all, I want to apologise to Mr Bryson (Although, I think, he will not read it), I thought he had made a 'typo' using the word million instead of billion, when he referred to the age of the earth. I was taught in school that a million millions make a billion, but afterwards because Bill Bryson had used American language in his book, I wondered whether Americans calculated a billion differently.
I 'Googled' it and to my surprise the following came up. 'Previously in British English (but not in American English) the word "billion" referred to a million millions (1,000,000,000,000). However, this is no longer the case, and the word has been used unambiguously to mean one thousand million (1,000,000,000) for some time.'
Now, after the apology,
What is DNA?
For the next 50 years, the common assumption that the material -- now called DNA -- had a subsidiary role in matters of heredity. DNA could only gain importance if its role was more important than prevailing thought allowed. By the early 1900s, scientists were still along way from understanding the confused business of heredity. Thomas Hunt Morgan found, when he was doing experiments with fruit flies, there were repeatable mutations -- a fly with white eyes rather than the usual red ones. Morgan and his assistants were able to generate useful deformities, eventually proving that chromosomes were at the heart of inheritance.
However, the next problem was the enigmatic genes and the DNA that composed them. These were much trickier to isolate and understand. What was certainly true that something associated with chromosomes was directing cell replication.
In 1944, after 15 years of research, a team, led by a Canadian named Oswald Avery, proved that DNA was far more than a passive molecule and almost certainly was the active agent in heredity. Soon the race was on to find the structure of DNA.
Linus Pauling, one of America's leading scientist, in the 1950s and 60s, became convinced that the DNA structure was a triple helix, not a double one, and he never got onto the right track. Instead, the victory fell to a quartet of scientists in England. Maurice Wilkins, Rosalind Franklin, Francis Crick and James Watson, an American, working in England. They assumed, correctly, that if could determine the shape of a DNA molecule, you could see how it did what it did.
The 25 April 1953 edition of 'Nature' carried an article by Crick and Watson, titled ' A Structure of Deoxyribose Nucleic Acid' (DNA). Watson and Crick's discovery wasn't confirmed until the 1980s. Even now, there is a great deal about DNA that we scarcely understand.
One interesting, humbling point, Bill Bryson makes in his book, and I quote --
'Remarkably, we are even quite closely related to fruit and vegetables. About half of the chemical functions that take place in a banana are fundamentally the same as the chemical functions that place in you.'
Here is a great video on the subject - 'The Origin of Life Made Easy' (editor).