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Anybody who teaches human evolution is inevitably asked: Are we still evolving? The examples of lactose tolerance and duplication of the amylase gene show that selection has certainly acted within the last few thousand years. But what about right now? It’s hard to give a good answer. Certainly many types of selection…
In response to these distasteful episodes of racism, some scientists have overreacted, arguing that human races have no biological reality and are merely sociopolitical “constructs” that don’t merit scientific study. But to biologists, race—so long as it doesn’t apply to humans!— has always been a perfectly…
We’ve always perceived ourselves as somehow standing apart from the rest of nature. Encouraged by the religious belief that humans were the special object of creation, as well as by a natural solipsism that accompanies a self-conscious brain, we resist the evolutionary lesson that, like other animals, we are…
The way we discovered how species arise resembles the way astronomers discovered how stars “evolve” over time. Both processes occur too slowly for us to see them happening over our lifetime. But we can still understand how they work by finding snapshots of the process at different evolutionary stages and putting these…
And when we think of why we feel that brown-eyed and blue-eyed humans, or Inuit and !Kung, are members of the same species, we realize that it’s because they can mate with each other and produce offspring that contain combinations of their genes. In other words, they belong to the same gene pool. When you ponder…
We can even see the origin of new, ecologically diverse bacterial species, all within a single laboratory flask. Paul Rainey and his colleagues at Oxford University placed a strain of the bacteria Pseudomonas fluorescens in a small vessel containing nutrient broth, and simply watched it. (It’s surprising but true that…
But “laboratory” adaptations can also be more complex, involving the evolution of whole new biochemical systems. Perhaps the ultimate challenge is simply to take away a gene that a microbe needs to survive in a particular environment, and see how it responds. Can it evolve a way around this problem? The answer is…
... moving randomly through space, like dust motes in a sunbeam, colliding, hooking together, forming complex structures, breaking apart again, in a ceaseless process of creation and destruction. There is no escape from this process. ... There is no master plan, no divine architect, no intelligent design. All things…
Vestigial genes can go hand in hand with vestigial structures. We mammals evolved from reptilian ancestors that laid eggs. With the exceptions of the “monotremes” (the order of mammals that includes the Australian spiny anteater and duck-billed platypus), mammals have dispensed with egg-laying, and mothers nourish…
Another curious tale of dead genes involves our sense of smell, or rather our poor sense of smell, for humans are truly bad sniffers among land mammals. Nevertheless, we can still recognize over 10,000 different odors. How can we accomplish such a feat? Until recently, this was a completely mystery. The answer lies in…
And the evolutionary prediction that we’ll find pseudogenes has been fulfilled—amply. Virtually every species harbors dead genes, many of them still active in its relatives. This implies that those genes were also active in a common ancestor, and were killed off in some descendants but not in others. Out of about…
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…
Knowing what we know from X-ray and related studies of the fibrous proteins, how they are built from long polypeptide chains with linear patterns drawn to a grand scale, how these chains can contract and take up different configurations by intramolecular folding, how the chain- groups are penetrated by, and their…
Of course there were scientists who thought the evidence favoring DNA was inconclusive and preferred to believe that genes were protein molecules. Francis, however, did not worry about these skeptics. Many were cantankerous fools who unfailingly backed the wrong horses. One could not be a successful scientist without…
Meantime, let no man be alarmed at the multitude of particulars, but let this rather encourage him to hope. For the particular phenomena of art and nature are but a handful to the inventions of the wit, when disjoined and separated from the evidence of things. Moreover, this road has an issue in the open ground and…
Brain wiring begins with the outgrowth of axons. Once a newborn neuron has migrated, planting its cell body in a permanent position, it sends out a fine axon shoot with an enlarged tip known as a growth cone. At the end of the growth cone are about a dozen long tentacles that shoot out in all directions and act like…
Each individual's genome, in any one generation, will be a sample from the species database. Different species will have different databases because of their different ancestral worlds. The database in the gene pool of camels will encode information about deserts and how to survive in them. The DNA in mole gene pools…
Caenorhabditis elegans was chosen in the 1960s as an ideal experimental animal by the formidably brilliant South African biologist Sydney Brenner. He had recently completed his work, with Francis Crick and others at Cambridge, on cracking the genetic code, and was looking around for a new big problem to solve. His…
A Mendelian gene is an all-or-nothing entity. When you were conceived, what you received from your father was not a substance, to be mixed with what you received from your mother as if mixing blue paint and red paint to make purple. If this were really how heredity worked (as people vaguely thought in Darwin's time)…
It is clear, however, that the cause of homosexuality lies in some unusual balance of hormonal influence in the womb but not later on, a fact that further supports the idea that the mentality of sexual preference is affected by prenatal sex hormones. This is not incompatible with the growing evidence that…