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There are many hypotheses on language and IQ evolutions, but many failed to explain sex differences of IQ. Some discussions presuppose that only Homo has language and that this appeared suddenly. Molecular level evolution does not support any sudden appearance of language. Bipedality amongst Homo was a factor in the evolution of many modem aspects of Homo; changes in copulation behavior contributed to the evolution of language; bipedality produced a larger brain, but blocked enlargement of the parturient canal and retarded further increases in the size of the brain. The female Homo was forced to deliver the neonate in a state of neoteny. Females further evolved language in order to take care of the infants. Male Homos accelerated food acquisition activities to provide the energy required to maintain a larger brain. The male Homo lost the initiative in sexual intercourse at female's mating season and began to depend on language from the female as a signal for mating. Females who acquired the initiative in copulation begun to select male partners by their ability to provide food and security. By this sexual selection, the evolution of language was accelerated. Neoteny, although physically disadvantageous, assisted neural development. Homo developed the ability to accumulate more information, a process in which language played a crucial role. Key Words: Homo Sapiens, evolution, language, neural development, intelligence, bipedality, copulation. Introduction Although there have been hypotheses on evolution of language which comprises a quite important part of intelligence, many of these explained this evolution in terms of early human collaboration for the purpose of hunting, escaping from dangerous animals, and other production activities which were primarily engaged in by males (Kimura, 1987). The hypotheses failed to explain the sex differences in verbal and performance IQs as reported by many researchers (Rushton, 1992; Halpern, 1996, 1997; Lynn, 1996; Lynn, 1998; Sanders & Wright, 1997). In addition to the psychometric data on sex difference, there is evidence of sex differences in brain anatomy (Reiss, et al., 1996; Shaywitz, et al., 1995; Sanders, 1998). Evolution of performance IQ is explainable by hunting and other production activities, but that of verbal IQ is not explicable by production activities. The higher verbal IQ of females and the common sense of talkative females must be explained by evolution pressure on females. In the beginning was the word! There are researchers who consider that language is a unique ability acquired only by mankind (Chomsky, 1988; Pinker, 1994). These researchers believe that language appeared very recently in the history of the evolution, as a result of one or more sudden mutations. However, molecular genetics does not support such rapid evolution by mutation. Mutations are almost always dangerous for the existence of a species, and the probability that positive, not dangerous, changes result from any specific mutation is extremely small. Molecular genetics confirms that the evolution of language did not happen suddenly. Behavioral level evolutional hypotheses should be consistent with the evidence provided by molecular evolution. This paper discusses presuppositions which should be considered in building evolutional hypotheses consistent with molecular genetics, then presents hypotheses concerning the possible evolution of sex difference in intelligence. Molecular-Level Evolution Leakey (1994) summarized three hypotheses on the evolution of languare proPosed from the archeological, brain-anatomical, and speech-organic points of views. (a) From archeological remains it is hypothesized that language ability appeared at the early stage in the evolution of Homo, stayed at a relatively lower functional level during most of the prehistoric era, and drastically improved in more recent times. (b) From the anatomical evidence of the brain it is hypothesized that language ability evolved gradually. …
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