According to the WHO, some 171 million people suffer from diabetes mellitus, and as Walsh has spelled out in his review, insulin therapy is absolutely essential for the survival of those with type I diabetes. It is also used to help control the more common type 2 diabetes as well.
Queen Victoria’s physician first noted in the 1800s that there were crystals in the pancreatic tissue of deceased diabetics. And research shows that dogs developed diabetes within 2 days of having their pancreas removed. In 1921, Banting and Best discovered that extracts from a region of the pancreas called the islets of Langerhans could revive diabetic dogs, and in 1922 after testing this extract on each other, they administered this crude insulin preparation to a diabetic patient, beginning the era of insulin therapy. You can read a summary of this work in a paper by Bliss.
Early production of insulin by Eli Lilly and Nordisk International relied on the extracts of slaughterhouse animals, and work continued for some years on methods to purify this relatively crude insulin extract. The problem was that extracts from pigs and cattle could be allergenic, and thus not all diabetics could use them.
Human insulin was sequenced in 1960 by Nicol and Smith, and it was found to differ from bovine insulin by 3 amino acids, and from porcine insulin by 1 amino acid. Work immediately begin on removing that amino acid in the 1970s and early 1980s. However, the pancreas of a single pig can only provide enough insulin for 3 days for a single diabetic.
Biosynthetic insulin was first developed by Chance and Frank in collaboration with Genentech in 1978. Initially different strains of E. coli were used to produce the A and B chains of insulin, and they were then combined chemically thereafter. Later, a single bacterial strain was used to produce the complete chain. A more modern method using genetically engineered yeast strains (Saccharamyces cerevisiae). Such insulins were approved for human use by the FDA in 1982.
It is now possible to create fast-acting and long-acting insulins to be administered under different circumstances, leading to prandial insulin therapy.
Today, all human insulin products are produced using genetically engineered yeasts and other bacteria, and it is perfectly possible to create exact copies of human insulin much less available using animal extracts.
Meanwhile, singer Neil Young is going about the U.S. promoting his album, The Monsanto Years, which has been heavily criticized for its inaccuracies. More to the point, Neil Young suffers from diabetes and takes genetically engineered insulin daily, even while railing against the techniques of genetic engineering that are keeping him alive. Sometimes looking into the science is really worthwhile.