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DNA directs the construction of strings of chemicals; those chemicals influence the configuration of the whole organism; that configuration influences how likely it is that the organism will reproduce and keep spreading more copies of the code.
The genes mutate enough through enough generations, and you get individuals that can no longer reproduce with each other; they’ve become separate or a new species.
Enormous flood-basalt volcanic eruptions, similar to the ones in Siberia and India, have poisoned the globe with dust and noxious gases at least fifteen times during known geologic history.
An isolated population is where new species are likely to emerge, and that’s exactly what happened.
Now the evidence shows that our ancestors and Neanderthals not only were alive at the same time, but apparently they interacted. They may have traded with each other, but that’s not all they did. Groundbreaking genetic work by Swedish biologist Svante Pääbo and others shows that the two kinds of protohumans had sex with each other. We were hardly more different than those two breeds of London mosquitos.
This impulse toward morphological classification is what inspired the Swedish zoologist Carl Linnaeus to create the naming convention that biologists still use to categorize every known species.
If their physical configurations are different but their functions are similar or even exactly the same, those species are only distantly related. If the configurations of organs and bones are nearly the same, they are closely related even if their shapes are rather different.
In physics, anything that flows is considered a fluid. Thus water and maple syrup are fluids, but so is air.
This business of homology is one of the absolutely most compelling indicators of the process of evolution. Just by looking at our bones, you can tell that we must have something in common with bats and birds, and even pterosaurs, the flying reptiles that lived at the same time as the dinosaurs.
We say fish are cold-blooded, or exothermic, meaning “temperature from the outside.” A marine mammal like a dolphin is warm-blooded; it has systems to keep itself at almost exactly the same temperature all the time, just like us. It uses calories to maintain that to be sure, but it can metabolize food efficiently, because its digestive chemical reactions are in a warm place. We say it is endothermic (“temperature from the inside”), just like us.
Feathers, scales, and hair all start from the same kinds of cells.
Each of us, snakes, birds, and people, has the ability to produce structures made of keratin, the natural plastic that is a snake’s scales, a bird’s feathers, and your hair and fingernails. Researchers have looked ever so
But now consider the B-2 bomber airplane; it has no vertical tail, no tail at all. Military tacticians wanted to eliminate the vertical tail, because radar would bounce off of it easily.
But here’s a crucial point: At the time when Archaeopteryx lived, it wasn’t a transitional anything, or a half anything. It was a creature well adapted to its environment. To a human designer, Archaeopteryx looks perhaps like an incomplete version of what we expect a bird to look like, because our expectations are set by the birds of today. In its time, Archaeopteryx was a perfectly complete competitor in its ecosystem.
mesothermic, meaning “heat from somewhere in between in and out.”
cannot emphasize enough the significance of this discovery. What we want as scientists, and as non-geek people who use the scientific method, is prediction. We want to come up with theories that allow us to make predictions about the future. It’s in our nature. Our ancestors, who did not bother to make predictions about the future, no doubt got very quickly outcompeted by other ancestors who could predict seasons, the movements of herds of prey, and the growth of food plants.
Light and heat are the same energy, just at different wavelengths and often at different intensities.
Apparently, our closest relatives, the chimpanzees, suffer a few days of depression or mourning, when a member of their troupe or barrel dies.
It could be radiation from some radioactive elements in Earth’s crust that caused a mutation. Sometimes viruses get into the reproductive cells of an organism and modify its genes. Virus manipulation can also be exploited
corn plants so they are tolerant of aggressive weed killer, for example.
This is called “genetic drift.” If the genes drift a little at the same time that there’s a change in the environment, the drifted genes may be the only ones that make it through.
If you believe public opinion polls, about half of the American public does not accept the proposition that life on Earth—including humans—is the product of billions of years of natural evolution.
Medical treatments have improved drastically, and evolutionary research is a major reason why.
For instance, we’ve discovered that cancer evolves. Cancer cells can mutate in the body of a patient, so that malignant cells find new ways to get a supply of blood and become resistant to our anticancer drugs.
We can use hormones from other animals—like insulin derived from pigs—to treat people because we came to understand our common ancestry.
Most Earthlings are microorganisms. You probably have no trouble accepting that. Now try this: Even the majority of the cells in your body are microorganisms.
They outnumber the cells of your body by 10 to 1. Those microbes are living, metabolizing chemicals, producing
waste chemicals, and interacting with each other. Collectively, they are known as your microbiome. You are their ecosyste...
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In general, the known antibiotics are toxins or chemical inhibitors produced by other types of organisms. Penicillin, for example, comes from a fungus, which is quite a bit different from a bacterium. Somewhere along the way, the mold Penicillium notatum chanced upon a combination of chemicals that disrupts the cell walls of a great many bacteria, which enables the fungus to advance its hyphae (fungal tendrils) without getting attacked, at least not successfully attacked. Being an organism that is different from a bacterium, a fungus can carry an antibiotic—in this case cell-wall-disrupting
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The general trick is to capture or get samples of the flu viruses infecting people in the Southern Hemisphere during their winter and prepare vaccines. It is an evolution-driven health system that almost everyone takes for granted.
Once your body recognizes an unwanted intruder—an infectious agent—it can send antibody proteins to wrap up the virus and pry it apart.
Bacteria take chemicals out of the environment to run their metabolism. After consuming the right amount of the right chemicals, bacteria have enough chemical energy to reproduce. They do that by splitting themselves in half. Of course, it’s a bit complicated biochemically speaking, but the idea is just that. We call it binary fission—splitting in two. That would be fine for the bacteria, but as they reproduce and metabolize the chemical environment around them, certain of them produce miserable toxins that make us sick.
The molecules that pathologists craft and chemical engineers work to mass-produce in oil-drum-sized “reactors” are what we generally call antibiotics. Perhaps the most famous among them is penicillin.
The more of these drugs we use, the more chances infectious bacteria have to come in contact with them, and the more likely these bacteria are to come up with descendant strains that are able to chemically protect themselves from the effects of the drugs.
That is to say, if your doctor gives you a two-week course of antibiotics, be sure to follow it all the way through, even if you start to feel fine in just a few days. Otherwise, you will probably not have killed all the bacteria that are in you, and the ones that are still hanging around will probably have a tendency to be immune to the antibiotic. They may not have complete immunity, but a fractional resistance will be passed on to subsequent generations of your germs, and they will be resistant to the same drug after you’ve passed your infection along to some other hapless victim and
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More precisely, they turn to game theory, a system of thought that breaks down behavioral costs and benefits in specific scenarios.
The most famous of the evolutionary games is the Prisoner’s Dilemma, formalized in 1950 by mathematician Albert Tucker, who specialized in what’s called game theory.
Game theory is just another way of probing the ways in which evolution has instilled altruistic instincts in all of us.
If someone else has acquired a new phone or lawn mower that clearly performs better than the one you’re using, you want it. From there, it’s a small step to feel the urge to be out in front, to make other people want what you’ve acquired. It costs you something, but you’re sending a signal—an evolutionary signal—flashing across deep time.
Today, farmers cede an average of 13 percent of their crops to insects. It is a serious, serious business.
GMOs end up carrying combinations of genes that would not naturally occur inside the cells of any organism. Scientists armed with a rich understanding of the DNA molecule have managed to combine genes from species that would never cross paths in nature, species that could never even be successfully “crossed” in the Darwinian sense by human breeders.
There were some chemicals on the ends of her chromosomes called “telomeres” that were shorter than researchers would expect in a newborn.
A cell that forms the body of an organism is called a somatic cell. Most of your cells are somatic; the only exceptions are stem cells and reproductive cells.
There is no question that the genetic modification of crops has enabled farmers to feed a great many more people using just a little bit more land. The reduction of losses to pests makes for an almost 30 percent increase in farm yields compared to a century ago.
If nothing else, the ubiquity of corn and corn syrup has helped to create the weird situation in the developed world, the U.S. especially, of fat people who are malnourished.
But it goes further than that: Scientists know enough about human DNA that they could, in principle, clone a human being and bypass the entire billion-year evolution of sex.
Cloning doesn’t give you a perfect copy, nor is the process instantaneous.
Cloning eliminates the variations that are the raw material of natural selection, replacing them with perfect genetic predictability … in principle, at least. At this point researchers have cloned about two-dozen different species. Nobody has cloned a human, yet—at least, no one has admitted to it—but the process would surely work the same way as it did with Dolly.
This fundamental insight that living things produce a surfeit of eggs and sperm, more than can survive, goes back to Darwin’s work on competing populations and figures prominently in any understanding of biology and evolution.
For me, this makes every baby that much more precious—after the egg successfully develops and a baby is born, not before the egg even attaches to its mom.
