Medical hypotheses
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Degenerative disc disease (DDD) is a major health problem worldwide. Both Modic lesions and Schmorl's nodes are considered to correlate with DDD such as low back pain. Modic lesions are the changes of degenerative vertebral endplate and adjacent bone marrow observed on magnetic resonance imaging and are divided into three types. Modic type III lesions are thought to represent extensive subchondral bone sclerosis within the bone marrow of adjacent endplate. The pathological performance of Schmorl's nodes is cystic lesions around indistinct sclerotic margins and beneath the cartilaginous endplate. Coincidently, there are many similarities between Modic type III lesions and Schmorl's nodes including pathological appearances, pathogenetic location and related diseases. ⋯ This hypothesis explains the possible pathologic process of Modic type III lesions and Schmorl's nodes. If the hypothesis were conformed, Modic type III lesions and Schmorl's nodes will be rediscovered, which provides the new basis for the clinical treatment of DDD. In additions, this hypothesis also has crucial significances for the classification of Modic lesions.
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Humans are an unusual species because they exhibit an economic division of labour. Most theories concerning the evolution of specifically human intelligence have focused either on economic problems or sexual selection mechanisms, both of which apply more to men than women. Yet while there is evidence for men having a slightly higher average IQ, the sexual dimorphism of intelligence is not obvious (except at unusually high and low levels). ⋯ However, the effect of maternal IQ on child mortality would probably only be of major evolutionary significance in environments where childhood mortality rates were high. The modern situation is that population growth is determined mostly by birth rates; so in modern conditions, maternal intelligence may no longer have a significant effect on reproductive success; the effect of female IQ on reproductive success is often negative. Nonetheless, in the past it is plausible that the link between maternal IQ and child survival constituted a strong selection pressure acting specifically on women.