DNA as Evidence of Common Ancestry

By sequencing the DNA of various species and measuring how similar these sequences are, we can reconstruct their evolutionary relationships. This is done by making the entirely reasonable assumption that species having more similar DNA are more closely related—that is, their common ancestors lived more recently. These molecular methods have not produced much change in the pre-DNA-era trees of life: both the visible traits of organisms and their DNA sequences usually give the same informatio...

 Cross-Species Milk

Our notions of mother's milk come from what we see, and for most of us the milk we see is cow's milk, a brilliant white liquid. But milk from other species looks quite different—kangaroo milk, for example, is pink. But whatever the hue, breast milk is species-specific; that is, the composition is finely tuned to the particular growth and maturational needs and digestive system of the young of each species.^ ^ For example, cow's milk is higher in volatile fatty acids than human milk, and hum...