Meet the Clydesdale. The Clydesdale breed once almost faced extinction. Even though there is little practical use for heavy horses today because their muscle power has been replaced by machinery, breeders and enthusiasts have ensured that the breed is increasing, rather diminishing in numbers.
1 Over the three decades, the twin birth rate rose by 76 percent, from 18.9 to 33.2 per 1,000 births (or from 1.9 percent to 3.3 percent of all births) (Figure 1). 2  Increases in the twin birth rate averaged more than 2 percent a year from 1980 through 2004 (peaking at more than 4 percent from 1995 to 1998).
Medicine: Viability of Twins. Â¶About one confinement in every hundred produces twins. The U. S. currently contains almost 4,000,000 twinsâ600,000 male pairs, 625,000 female pairs, 635,000 mixed pairs. For some reason which biologists are trying to fathom mixed twins predominate at birth. Â¶ A pair of male twins may expect to live jointly until the age of 46, mixed twins until the age of 48, female twins until the age of 50.