Mammary Glands
Thus the organic adaptations of the female, may be complemented by the behavioural adaptations of the young. In general, the female's organic and behavioural adaptations increase with the brain mass/body mass ratio.
The mammary glands of the Human specie are different from those of the Chimpanzee or Gorilla. These apes have relatively flat breasts and long nipples. This meets the needs of their young, who tend to have marginally protruding jaws and palates -- which need a proportionately long nipple. By contrast, the human breasts tend to be more bulbous, with a much shorter nipple.
In this context, there is no reason to believe that the needs of the hominoid (Ape) young varied very greatly, during the period of pre-hominidal evolution. However, when there are substantial, physiological variations of either mammae nipple size; or testes size; or penis size; it is reasonable to assume that these were caused by evolutionary adaptations - to changes in mating, reproduction, or infant-rearing systems.
In Chapter Five, the author proposed that the adaptation to the requirements of a
subtropical climate involved a reduction in body size, which led to a change in the specie’s head to body ratio. This led to the extension of the period of helplessness of the hominid baby.
In this regard, it will be immediately apparent that a helpless hominid baby would need some maternal assistance to reach its mother's breasts. The mother would have to pick up its baby, and guide the baby's mouth to her nipple. The baby would be able to 'forage' for the nipple itself, and start suckling -- as both of these are reflex actions. However, the mother would still have to support the baby's head during feeding.
Even a helpless baby could still hang on to its mother, by holding on to her skin, or fur, providing the baby's hands and feet were guided to the right place -- and provided its hands and feet were kept open before contact was made. Infantile gripping is another reflex action, and hominid babies would be able to hang on to their mothers -- if they were placed in the appropriate position, in the appropriate way.
Unfortunately, it is not normal for babies to open up their hands, if they are very young --because this requires cognitive ability. A young baby's hands tend to remain clenched, and they cannot grip anything unless it is physically placed into the palms of their hands.
Forward facing nostrils
Thus during suckling, a hominid baby would depend upon its mother for support, and the mother would tend to hold the baby's head close to her breast. This would tend to position the proto-hominidal, forward-facing nostrils of a hominid baby very close to the chest wall of the mother. As a result, an anxious, or careless, or frightened mother, could accidentally suffocate her baby as she pressed its head against her breast.
The hominoidal Ape baby does not stiffer from this problem because it can climb up, and hang on to its mother to suckle. Such a baby can feed itself without the need for maternal support. If its forward-facing nostrils are accidentally blocked, it will immediately move its head back by reflex action.
A helpless, hominid baby could not do this, as its head would be pressed in to its mother's breast by the mother's hand. It could not cry out, as the nipple would be in its mouth.
Instead, it would silently suffocate.
It is proposed that the frequency of early hominid infant mortality, due to accidental suffocation, would be sufficient to lead to evolutionary adaptations by both babies and mothers.
In this context, it is proposed that the baby's nose would gradually change, so that the forward-facing nostrils of the hominoid Apes would be replaced by the downward facing nostrils of the present day humans.
It is further proposed that mammae of early hominids would be supplemented by fat -- to project the female nipple well clear of the chest wall. This would prevent the nose of the baby from being squashed up against the chest of its mother.
This organic adaption illustrates a possible example of series evolution, where one adaption can create a demand for another, consequential adaption.
Bulbous, protuberant breasts
For example, the evolution of bulbous, protuberant breasts could lead to further suffocation, albeit on a lesser scale. This is because the soft skin and fat of the breast, could envelop the nose of the baby and lead to its suffocation.
It is proposed that a further evolutionary adaption would involve the dilation of the blood vessels surrounding the mammary gland, and this would make the breast relatively stiff.
The dilation of the blood vessels would be stimulated by the suckling action of the baby, and the stiff breast would prevent the baby's face and nose from being enveloped by the breast's soft, fatty tissue.
Another potential threat to the helpless baby would be the long, hominoidal nipple. This could easily choke the baby, as its head was pressed in to its mother's breast. It is proposed that this danger would lead to the evolution of the short, hominidal nipple.
These are minor changes of physiology, but quite typical maternal adaptations which meet the needs of the young. If the babies die, the specie dies. In this regard, the suckling of young babies is a very critical element in mammalian survival.
As a result, it is reasonable to deduce that any perceived changes to a baby's mouth, palate, lips, gums etc. , and its nose -- if this is close to the mouth, will be due to a change in infantile, or maternal demands.
It should be noted that it is very much easier for an adult to adjust to the demands of an infant, than the other way round. As a result, most evolutionary changes involving mammary glands and nipples, are due to adaptations by the adults to the needs of their infants.
http://www.jdwaters.info/HAAB%20Acro/c6to.pdfIt's not that Apes haven't been seen walking through water or that some do have protuberant breasts......but those are exceptions, not the rule.
If I hold a cookie out, my dog will magically become bipedal too. If I took a picture of it, could I ask who started the 'rumor' that dogs can't be bipedal?