Using an average age of 5,000 years for each language family, and an average branching rate of 1.6 languages per family, it would take at least 100,000 years to create the existing global language diversity. Of the 300 language families in the world, over a third (130) are found in Australia and New Guinea. This area of the world was initially populated no earlier than 50,000 years ago.
If we were look for the essence of intelligence, one might consider cleverness, versatility in solving problems, or foresight and planning. A particularly intelligent person often seems to one that is "quick" to juggle ideas and narrow in on a solution or response. This often requires the ability for versatility. It is interesting to note that most animals tend to become specialists when it comes to making choices. This is particularly true in terms of diet choices. Yet versatility can be an asset while not always so.
Consider the case of chimpanzees in Uganda. It is not uncommon for these chimps to arrive in an area of the forest where monkeys have efficiently and speedily stripped the trees of edible fruit. The chimps can turn to eating termites or even catching and eating one of the monkeys. This is in a limited way a case in point for versatility. However, one has to recognize that the monkeys with their specialized response compete very well and severely limit the number of chimpanzees. It is interesting to note that the chimps have more than twice the brain size of the monkeys so what does this imply in terms of brain size as well as intelligence.
To understand why humans may be so "intelligent", we need to understand how we process information. To best understand this we must focus on how we process language. Language is best defined by our ability to create syntax - the orderly arrangement of verbal ideas. Chimpanzees in the wild use about three dozen vocalizations to convey about the same number of different meanings. They may repeat sounds to convey greater intensity of an idea, but they do not string together three sounds to create a sort of vocabulary. In contrast, we use about three dozen sounds (known as phonemes). We utilize these sounds in sequences and combinations to create content. That is, we use the sounds to create words and then we use words in sequences (syntax) to convey meaning. The critical threshold is that we use combinations of sounds rather than a "one sound - one meaning" system for communication.
The importance of syntax is that it creates a treelike set of rules of reference that enables us to communicate quickly - who did what to whom, where, when, why and how. Children acquire syntax effortlessly by listening.
Language may be the key to understanding how we not only use short-term planning as well as long-term memory to allow us to make crucial decisions. Social life perhaps is the key to providing individuals with the chance to mimic and learn useful ways to adapt. Useful discoveries by one individuals can be passed on to others via socializing. Anthropologists recognize primates to be highly sociable creating a vehicle by which to pass on meaningful behaviors that enhance our ability to survive. Language is something that requires both physical and mental capacities to merge. Our throat structure must develop the capacity to create a resonance chamber for sound production; our tongue must be able to articulate to create sounds we call consonants; and our brain must be able to assist in linking these physical capabilities with syntax and memory.
One must remember that there is a process of selection that would operate on our ability to create this breakthrough. First, the genetics must be present. Second, copies of these must be made and passed on to subsequent generations. Thirdly, one would assume that further variations would be created through mutations that continue to accumulate. Fourth, these variants would compete with relative success measured in terms of how frequently they are passed on to the next generation. Many of the new variants would be less successful and others more so. The real question may lie more in where the pressure for competition might arise. Consider that the increase in our brain size has occurred within the context of the Ice Age, the last 2.5 million years, and most of it in the last 1.8 million years.
What was the Ice Age? It was a period of extremes or oscillations between warm and cold. During one oscillation, for example, the temperature rose 13 degrees, rainfall increased by 50 percent and the severity of dust storms fell, all in the space of few decades. Cold periods began just as suddenly. Hominids and eventually early humans may have needed greater intellectual capacities to survive these radical changes. It is hard for us to envision that entire forests may have disappeared within several decades because of drastic drops in temperature and rainfall. While these new conditions may have lasted for generations, there was always a subsequent, and equally radical, change when warm rains returned with equal suddenness. This then may have been a critical aspect that placed intense pressures on hominids throughout the span of the Ice Age.
The evolution of anatomical or physical adaptations would
be hard pressed to key pace with dramatic changes such as these since they
could have occurred within individual lifetimes. It is more likely that
these abrupt fluctuations would have promoted the incremental accumulation
of mental abilities that conferred greater behavioral flexibility - versatility,
creativity, syntax, and memory. Each of these would concomitant upon genetic
counterpoints that enabled new variants in terms of behavioral responses.