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In mammals, including humans, sex is generally determined by the X and Y chromosomes. If a baby has a pair of X chromosomes, she’s a girl. If the baby inherits an X chromosome and a Y chromosome, he’s a boy. In birds, however, the situation is reversed. Female birds have a pair of unlike sex chromosomes while males…
Panchin knows the idea of cancer-derived animals sounds far-fetched — so much so that, in the paper, he and his co-authors refer to them as Scandals (an acronym for “speciated by cancer development animals”). [...] According to Panchin’s three-step scenario, a Scandal would start off as a cancer, but not just any…
The analogy is mathematically precise, and fascinating. In rough terms, it says that the process of natural selection resembles the process of Bayesian inference. A population of organisms can be thought of as having various 'hypotheses' about how to survive—each hypothesis corresponding to a different allele…
Physicists love to think about systems that take only a little information to describe. So when they get a system that takes a lot of information to describe, they use a trick called 'statistical mechanics', where you try to ignore most of this information and focus on a few especially important variables. For…
The trick of magnifying a normal creature to menacing size is all too common. The giant amoeba is a familar example; monster insects (or whole populations of them) even more so. It might pay an author with this particular urge to ask himself why we don't actually have such creatures around. There is likely to be a…
The need for an internal skeleton stems largely from the nature of muscle tissue, which can exert force only by contracting and is therefore much more effective with a good lever system to work with. I belittle neither the intelligence nor the strength of the octopus; but in spite of Victor Hugo and most other writers…
In 2007 two researchers, chemist Martin Hanczyc and artificial life scientist Takashi Ikegami, who were collaborating across disciplines agreed to test a hypothesis about the earliest forms of life (Hanczyc et al. 2007). They hypothesized that life’s precursors would need to move around their environment to take…
Television images are sometimes displayed on giant LED (Light Emitting Diode) hoardings. Instead of a fluorescent screen with an electron beam scanning side to side over it, the LED screen is a large array of tiny glowing lights, independently controllable. The lights are individually brightened or dimmed so that…
The central problem for any theory of the origin of replication is the fact that a replicative apparatus has to function almost perfectly if it is to function at all. If it does not function perfectly, it will give rise to errors in replicating itself, and the errors will accumulate from generation to generation. The…
Given the invasive nature of pregnancy, it’s perhaps not surprising that the primate womb has evolved to be wary of committing to it. Mammals whose placentae don’t breach the walls of the womb can simply abort or reabsorb unwanted foetuses at any stage of pregnancy. For primates, any such manoeuvre runs the risk of…
There is no authoritative definition of “species.” The most widely accepted definition describes a group of organisms that can procreate with one another and produce fertile offspring, but there are many exceptions. De-extinction operates under a different definition altogether. Revive & Restore hopes to create a bird…
The century of biology upon which we are now well embarked is no matter of trivialities. It is a movement of really heroic dimensions, one of the great episodes in man's intellectual history. The scientists who are carrying the movement forward talk in terms of nucleo-proteins, of ultracentrifuges, of biochemical…
Everything is made of atoms. That is the key hypothesis. The most important hypothesis in all of biology, for example, is that everything that animals do, atoms do. In other words, there is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to…
If we possessed a thorough knowledge of all the parts of the seed of any animal (e.g. man), we could from that alone, by reasons entirely mathematical and certain, deduce the whole conformation and figure of each of its members, and, conversely if we knew several peculiarities of this conformation, we would from those…
It is against the background of conflict and confusion in the relations of science and society that we find ourselves confronted with a crisis in the history of mankind, and particularly in the history of human government. It is a crisis arising from the rapidly increasing power given to man by science. It is a crisis…
Every vitamin is made by living cells — either our own, or in other species. Vitamin D is produced in our skin, for example, when sunlight strikes a precursor of cholesterol. A lemon tree makes vitamin C out of glucose. Making a vitamin is often an enormously baroque process. In some species, it takes 22 different…
In 1838, Matthias Schleiden, a botanist, and Theodor Schwann, a physiologist, both working in Germany, had claimed that all living organisms were built out of fundamental building blocks called cells. Borrowing and extending this idea, Virchow set out to create a “cellular theory” of human biology, basing it on two…
You really don't have to worry about one part of your laptop going rogue and trying out something on its own that the rest of the system doesn't want to do. No, they're all slaves. If they're agents, they're slaves. They are prisoners. They have very clear job descriptions. They get fed every day. They don't have to…
Here's a simple question: Why do you weigh more when you go to sleep than when you wake up? Because you do... You can check this yourself. Somehow, while doing absolutely nothing all night but sleep, you will wake up lighter. [...] All night long, every time you breathe out, a bunch of carbon atoms, formerly inside…
Life began in water, and every single function of life takes place in an aqueous environment. A profound way of classification in chemistry is the relation and interaction between molecules, or groups within molecules, and water. Molecules (or parts of molecules) can attract water in which case they are called…