(On Screen): Biologists now generally accept what is known as the "Five Kingdom" model, which divides all known life on Earth into one of five large kingdoms. They're called Monera, Protista, Fungi, Plantae and Animalia. The big division there is between the first one and all the others, because Monera comprises all prokaryotes, whereas the other four kingdoms are eukaryotic, which is to say that they have a nucleus and organelles. For most of the history of life on earth, all life was prokaryotic, and evidence of prokaryotes exists in the oldest rocks we know of. It's widely believed that the processes involved in development of the earliest prokaryotes were quite rapid, and that they appeared nearly as early as it was possible for them to appear.
And proceeded to change the environment, because among the very early tricks they learned was photosynthesis. As a result, they eventually changed the atmosphere of the planet from reducing to one dominated by oxygen, and by so doing eliminated the conditions that might have made another independent creation of life possible. So all life is thought to derive from one single origin.
However, the switch to eukaryotes wasn't as easy, and it probably only happened in the last few hundred million years.
All of this is governed by evolution, of course. Jean-Baptiste Lamarck is widely thought of as being the father of Evolution, because he was influential in arguing for it as an aspect of how life developed. He also proposed a mechanism for how it took place which was very clever and elegant and, most regrettably, not correct. Lamarck proposed that each generation passed on to the next the characteristics it acquired. So giraffes who strain to reach high leaves would stretch their necks, and their offspring would be born with longer necks.
Darwin eventually described the proper mechanism: some giraffes naturally had longer necks than others, and those were less likely to starve, and thus were more likely to breed and pass on their characteristics. Darwinian evolution by natural selection is inelegant, inefficient, very cruel and wasteful and, it turns out, true.
When reproduction was parthogenetic, then it meant that accumulation of favorable characteristics was not efficient. For two favorable mutations to appear in the same organism, it meant that the second had to take place among those organism who were descended from the one who got the first one.
When you had a large number of such organisms coexisting, then if there were disparate favorable characteristics among peers, there wasn't any way to get them into a single individual.
In many prokaryotes there actually is a way. Sometimes when they bump into each other, they'll temporarily fuse and exchange some of their cell protoplasm. Then they separate. This can actually happen between individuals of different species, and part of what they exchange when they do this is the plasmids suspended in the protoplasm. A plasmid is a small ring of DNA which is not part of the cell's chromosome, and once in a while, by sheer luck when this happens, one of the two cells may get a plasmid with a useful characteristic which it didn't previously have, and therefore will become better able to survive and compete.
Since the development of antibiotics in the 1940's, and the widespread use and abuse of them, disease-causing bacteria have faced a severe survival challenge. Inevitably, one of them somewhere gained the ability to resist penicillin, and other mutations gave other such bugs the ability to resist other kinds of antibiotics, and they did indeed do a certain amount of sharing with one another and there are now strains of some diseases which are resistant to more than one kind of antibiotic. In fact, there are a few strains out there which are now resistant to every drug we have, and can no longer be treated. That ability to trade genes back and forth between individuals is a major advantage.
After the evolution of eukaryotes, eventually some of them developed a new trick: sexual reproduction. Likely this was a gradual process, but no one knows for sure. However, as more and more organisms trade a larger and larger part of their genomes back and forth as part of the process of reproduction, what you get is bugs which are particularly well suited to play the Darwinian game. Once sexual reproduction appears, there's an evolutionary explosion, and the variety and quantity of life on the planet grows immensely. Sexual reproduction was an advantage because it was a lot more efficient than parthogenesis at accumulating favorable mutations in single individuals and at spreading them out within the whole population of the species.
Most kinds of plants are bisexual. Sometimes they have male parts separate from female parts, as in many conifers, and sometimes both appear as part of the same organ, as is the case in most flowering plants. Far more often than not, plants which are bisexual will end up being pollinated with their own pollen, but sometimes the pollen comes from another plant, and then the plant gets the chance to produce offspring who might gain advantages from both parent stocks. (Of course, the offspring might also gain the disadvantages of both, but such beings tend to die out and don't really affect the Darwinian game much.)
There is a lot of variation in this. In some cases individual plants may only develop male parts or only female parts. In some cases both develop but at different times. In a few cases the reproductive process is extraordinarily specific and may be entirely dependent on some particular insect species. Some cactuses and some orchids are totally dependent on specific wasp species for reproduction.
And there are a few very strange cases. Dandelions went through some rather odd mutation, some time back there, and while they still produce a flower, it no longer has pistils or stamens (respectively the female and male parts of a more normal flower). Once the flower withers, dandelions produce seeds parthogenetically. Dandelions no longer reproduce sexually, and that means they're now stuck on the slow evolutionary track of having to accumulate mutations within long family lines, without any intertrading. Fortunately for the dandelion species (and unfortunately for suburban homeowners everywhere) the dandelion had already become quite the survivor before this mutation took place, and they're still prospering. But if they're ever presented with a really serious challenge, their ability to react evolutionarily may not be up to it.
Kingdom Animalia has contributed an entirely new facet to this process, because large animals have brains. In many species of mammals and birds, parts of their behavior is learned rather than being driven genetically. It has been demonstrated, for example, that some kinds of song birds learn their song by hearing their parents sing it when they're chicks, even if they only hear it once. If they are raised in captivity and are never permitted to hear such a song, they do not sing properly.
In some animals the amount of behavior which is learned can be quite large. There are many places where animals can survive by working in groups far better than they could operating alone, and this is particularly true among large predators such as lions, wolves and African wild dogs. Lionesses who hunt in groups are far more likely to make a kill than those who hunt alone. They actually use strategies; most of them will sneak up on a herd of gnus or zebras on one side, and then a couple will reveal themselves on the far side of the prey herd, deliberately scaring the prey animals to flee towards their sisters who wait concealed. I don't know the extent to which that behavior is learned; I don't think it's been established.
But it has definitely been established that among African Wild Dogs that most of their pack behavior is indeed learned. They live in large groups, sometimes up to 50 at a time, and like many pack canines only a few members of the pack actually breed. In order for the pack as a whole to survive, the dogs have to cooperate, get along, and hunt in groups.
There was a program where a group of Wild Dogs were bred in captivity, and then released in a group in an area where no existing packs lived. They did not do well; most of them starved to death. They did not hunt properly, and they quarreled among themselves; it was not a success. The problem was that during captive breeding, the pups had not learned all the necessary lessons about how the pack operated that pups in the wild get.
For lack of a better term, this new feature of evolution probably has to be called "culture", and no species does it better than ours. In fact, we are so much better at it than any other species that it has ultimately ended up being our primary evolutionary advantage which has let us prosper and spread.
Our hominid ancestors, a few million years ago, were more or less quadrupedal the way that chimps and gorillas are now, and because of that were pretty much limited to arboreal settings. The essential change which set us on the path to our current form seems to have been the development of upright posture. The earliest hominids which are clearly part of our evolutionary line do not show any significant difference in brain size, but they show distinct changes in the shapes of their legs and pelvises which adapted them to bipedal locomotion.
Why did it matter? Probably because it meant you could move around while carrying babies and not be slowed. Chimps have to stay near trees because female chimps with babies have to use one arm to carry the baby, and thus are much slower. Their only safety from many kinds of predators is in the branches. When the hominids became bipedal, they were better able to exist on the grasslands, which opened up a large new ecosystem.
One possible sequence thereafter goes like this: once you can travel on two legs carrying babies, you can also carry other things. In particular, you can carry animal thighbones you've found. That means that in addition to gathering plant material for food and taking advantage of the occasional carrion, you can actively hunt. The apes were already omnivorous and had the enzyme complement to take advantage of meat as a form of food, and now they could actively hunt for it.
But they were small and weak, and their only real chance of success in hunting was to work in groups. The better able they were to coordinate and work together, the more successful they'd be hunting, and so there was an advantage in being able to communicate.
All of this makes larger brains more of an advantage. Making plans, the ability to consider the possibility of how things might be changed so as to be better, was very sophisticated. Learning how to create your own weapons, which might be better than what you could find, helps. So over a period of time you get evolutionary selection in favor of creatures who were smarter, better able to communicate with and cooperate with one another, and better able to transmit information.
Early on, hominids became sufficiently good at this that Homo erectus boiled out of Africa maybe a million years ago and settled all over the place in Eurasia. But the advances went on, and probably a hundred thousand years ago an entirely new form of hominid, Homo sapiens appeared in Africa who was far better at all these things. The new critters, sometimes referred to as the Cro Magnons, likewise boiled out of Africa and, eventually, became the only large hominid found anywhere.
The big advantage of humans was the ability to learn and to pass on that knowledge: culture. Humans, like wolves and lions, lived in groups and what you eventually begin to see is competition between those groups. Individuals were subject to evolutionary pressure, but you also had competition between tribes, small groups of humans who lived together and were usually genetically related to one another. Much of their success overall came because of the characteristics of the tribe, rather than the characteristics of individuals within that tribe. The members of the tribe maintained a body of knowledge which helped them survive.
Some of that was direct practical knowledge. Knowing about some specific kind of food, where it could be found, and how it might need to be processed in order to remove toxins or to make it more nutritious, was clearly valuable. Techniques for making weapons and learning how to use them was equally valuable.
Some of it was more indirect. As with the Wild Dogs, humans have to learn to live together. Groups of strangers put together, with no such experience, don't do anything like as well. Tribes might have religions, legends, dances, songs, rituals; these things served to bind the members of the tribe together so that the tribe as a whole would survive and prosper. There would be customs about what members of the tribe could and could not do with one another: how one selected a mate; how mates might live together; what kinds of behaviors were considered intolerable (i.e. "laws") and what kinds of punishments would be dished out to those who acted intolerably.
Different tribes might have different collective cultures. They might have different bodies of survival knowledge; different ways of making weapons; different religious beliefs and tribal bonding patterns. Due to their culture, some tribes as groups might be better able to survive than other cultures.
Though African Wild Dogs reproduce sexually, packs of dogs reproduce by fission. When a pack grows too large, some members will split off and found a new pack. They'll take with them the learned behavior patterns from their parent pack, so that knowledge passes from the original pack to both of its offspring.
Human tribes also reproduced by fission, in exactly the same way. When tribes became too large, some members would leave and move elsewhere. But human culture could change in other ways.
Though biological inheritance is genetic and biological evolution is largely Darwinian, cultural inheritance is Lamarckian. Each generation can add to, subtract from or alter part of the tribal culture before passing it on to the next generation, and that modification process is intelligent (because the members of the tribe are intelligent). So cultures adapt and change at a stupendous rate.
Moreover, cultures can partake of a form of cross-fertilization somewhat like how prokaryotes exchange genetic information. Tribes encountering other tribes may learn things from each other, consciously trying to absorb the best of what another tribe has to offer.
This wasn't always peaceful. It could be; neighboring tribes could get together for a feast and a lot of talking, or perhaps learn from one another as part of a long term trade relationship. But sometimes it was violent. If a tribe became large and needed to split, and if there was no uninhabited ground nearby, then they might engage in war and attack a neighboring tribe, killing all the men and taking the women and children as slaves. This would open new terrain for the victorious tribe to expand into.
The tribes and their cultures were thus super-organisms, engaged in competition at the level of the tribe, and tribes whose cultures better adapted them would generally defeat others whose cultures were less successful. Like all evolution this is an imperfect process and other factors played a part, so this is more a statistical generalization over a long period of time.
Tribal cultures spread and mutate; merge and split, and a lot of them died off. Some cultures were better adapted and started dominating, eventually becoming nations. Some tribes were conquered and forced to adopt the culture of their conquerors.
Pre-historical human culture reached a point of being throttled by transmission capacity long ago. There was a limit to how much information could be retained and passed on solely via oral tradition and direct example, and if you tried to keep too much there was a greater chance of transmission loss and harmful distortion.
Just as the development of sexuality causes an evolutionary explosion, it is the development of writing which brings about a human cultural explosion. Writing alleviates the capacity limit, and makes it possible for information to more easily travel in both space and time with far less distortion and loss. That's why I chose writing as being one of the four most important human advances in history.
In recent years, there's the beginning of study called memetics, where specific pieces of knowledge are thought of as memes which compete with one another in the virtual space formed collectively by the brains of every human alive.
The memetic evolutionary space is Lamarckian, and memes can crossbreed and mutate and are engaged in competition with one another. There seem to be characteristics of some memes which make them better adapted to spread, though perhaps not in any other way. For instance, religious or ideological memes which include a mandate on their followers to evangelize are more likely to spread than those which do not.
And in cultural competition, the ability and tendency to combine best-of-breed characteristics from competing lines to create a superior offspring is a big advantage. That gave sexually reproducing organisms an advantage in Darwinian evolution, and it gives memes and cultures an advantage in competition between tribes.
Tribes which become xenophobic, who reject any ideas or knowledge from outside, become the cultural equivalent of the dandelion, stuck in the evolutionary slow lane. Both will advance only through the slow accumulation of changes within individual lines; neither can take advantage of cross-pollination. And both are far less able to adapt if they ever face a critical challenge. On the other hand, cultures which are xenophilic, who seek out other cultures and readily absorb what they find there, tend to be particularly successful competitively. That process aids them in eliminating their worst and most disadvantageous characteristics, and makes them far more resilient in the face of serious challenge.
Evangelism and xenophilia aren't necessarily mutually exclusive; it's possible for both to exist in a given culture. But on a conceptual level they're in conflict. Evangelism derives from a belief that "we're better than they are", whereas xenophilia tends to require acceptance of the idea that "they might be better than we are in some ways". Of course, these can operate simultaneously in different conceptual areas without overlap; we might believe that our religion is the best one while simultaneously eagerly studying some other culture's art or foodstuffs or basic technology.
You can also get alternating phases of each over a period of years or centuries, where a given culture switches from one to the other and then back again.
But in general, what you find is that some cultures tend to be dominated by evangelism and they don't tend to be as open to outside ideas. Others tend to be quite xenophilic and don't tend to be quite so evangelistic. You can also get some which don't tend to either, which are smug and self-absorbed and are so contemptuous of outsiders that they feel little need to spread their ideas to anyone else.
Sexual organisms evolve faster and adapt better because they're better able to mix genetic information within the species. Cultures which are open to ideas and concepts from other places tend to be the most competitive.
And cultures which want to do this, who are prevented from doing so, are being artificially stunted. As the second part of this article will show, that's one of the big political issues in the world right now.
Update: Dave Tepper comments.
Update: Brian Tiemann dowdifies me.
Update 20030801: Marc Miyaki comments.
Update 20031228: Revisiting this months later, I discovered I got my paleontology slightly wrong. The first wave of hominids to colonize Asia probably left Africa between 1.5 and 1.8 million years ago, rather than 1 million years ago as stated above.