We try to answer in the first place to the first thing. The evolutionary tendencies that are observed in the hominids are included inside the called process of hominization, that is characterized by:
1) A tendency to the bipedism or straightened up position, that in the human species is reached fully. This tendency was practiced also in other fossils anthropoid primates, that lived in the trees and has been obtained imperfectly in the present anthropoid primates as gorillas and chimpanzees. Perhaps the change of habitat of our ancestors, the change of the forest with many trees to the savannah, with large open spaces to walk, as consequence, probably, of a climatic change, favored this biped tendency, although already it was aimed in arboreal primates. Another theory aims the existence of an aquatic phase of the human ancestor 5-6 millions of years ago, in the beginning separation of the remaining antropoid primates, when the African lands in the south of Ethiopia were flooded by the sea; in this amphibious environment, our ancestors would acquire the bipedism, the lack of hair and moore quantity of grease as others mammalian of the savannah. This it would explain the great quantity of grease of the human babies and its facility to be moved submerged in the water. The reduction of the tail is probable that be related to the acquisition of the bipedism.
2) A consequence of bipedism is the liberation of the ground of the anterior extremities; they were transformed into superiors. These extremities could be utilized to get and to catch food and tools; this fact favored the construction of implements and contributed to the development of the intelligence. The hands went itself doing less rough and with finer fingers if we compare them with those of other antropoids. Besides, the thumb, perfectly oponible to the remainders 4 fingers, was done more long than the other fingers. The nails tended to be reduced and the skin of the fingers, especially of the fingertips, accumulated many quantity of sensitive corpuscles, being done fine and delicate, very sensitive.
3) A change in the diet. This change are connected with the transition from the forests to the savannah. In these more open spaces, the vegetable food would be more scarce and our ancestors were obliged to complement its vegetarian diet with an animal diet, hunting animals in these more open spaces and having to be displaced more for such thing, which is probable that stimulated a bipedism increasingly more efficient. Also, the incorporation of meat to the diet enlarged the caloric contribution without necessity to eat so abundant and so frequent, as occurs to the vegetarian animals; this fact, perhaps provided more free time for other activities and what is more important, supplied more nutritive and caloric contribution to the brain, which could be developed with more facility.
4) A progressive development of the skull capacity, of 400 c c. in chimpanzees to 1.400 c c. in the human species, with the consequent increase of the volume of the brain, in relation to the remainder of the body and the consequent increase of the number of neurons. The number of these cells was seen favored by another parallel tendency of the cerebral surface that already appears in other mammals: the increase of the cerebral surface of the cortex: this introduce himself into the brain and give rise to the cerebral increase of internal surface; with this strategy, it is obtained a great increase of surface with a great deal smaller increase of volume and the nature has utilized it in other animal structures as for example the intestinal and pulmonary creases, etc. With this spectacular increase of neurons in the cerebral cortex, a greater intelligence was obtained. It could to package a great deal of information in a minimum space. All animals with certain intelligence, have big brains with internal folds (in the case of the mammals). The development of the intelligence led to of parallel form the development of a complex system of communication: the language spoken; it is the most elaborate system of emission of sounds in the animal communication that knows, although other animals, as birds, dolphins, whales, etc., have also developed complicated languages of communication, but these, although they can be more powerful in the communication to long distances, do not have the capacity of expression of diverse facts as the human language has it.
5) A growing "neoteny", that is: the humans conserve in adults childlike characters. This tendency favors a greater plasticity in the cells and permits a greater evolutionary flexibility and adaptability with respect to the environmental changes.
6) A progressive lack of hair in the body. This seems to be consequence of the protection of the body with clothes and skins; the reason is a greater intellectual development, or the aquatic phase of the human ancestor.
7) A transformation of the face. The binocular and stereoscopic vision is not exclusive of the man, therefore this is reached in other animals and in all the apes, included the hominids. The eyes adopt a position in a front level. A vision in relief is obtained although the space of vision is lost (it is covered less visual space) and to see the sides one must rotate the head. The arches of jaws are done more graceful and small with reduction of the teeth. This tendency is related with the evolution of the alimentary habits. The man makes omnivorous, and the teeth, already little specialized in the primates, specialize less in the man. When te man prepare and cook the food, facilitate its breaking and the teeth are done less powerful and are reduced in size and in number Besides, the hands serve to be catch the pieces of food to the mouth and the teeth and the jaws do not have to start them of their places of origin; this, it do the hands. In this way, from faces with small eyes, narrow fronts and long and prognates jaws, it is passed to faces with wide fronts and cleared, big eyes and reduced jaws and small mouths. The faces pass to be wide underneath and narrower by up to the contrary thing: wide and large by up, in the front and narrow underneath, in the jaws and mouth.
8) Respect to the organs of senses, the human species has these with an own development of its ancestors primates. The eyes permit that the man relates with the environment interpreting the visible luminous energy. They are the organs of senses of the most power in a air environment; they are the one that more long reach and the quickest (the environmental information through the light travels to enormous velocities); therefore is able to say that they are of the most perfect. The eyes are the organs of maximum development of all the senses in the man. The men are diurnal animals and so, they have managed to see colors. In the mammals this is obtained in primates, some carnivorous as dogs and cats, although in incomplete form and more clumsily, in rumiants. As a general rule, the animals that have bodies and livery of colors, see theese. Also, the vision of colors is developed in diurnal animals such as many birds, in some reptilian, fish, insects, etc. Also, as primates that they are, the humans have stereoscopic vision, perhaps as an inheritance of the arboreal primates. Nevertheless they have not developed a great visual sharpness neither a great vision in the distance and in wideness, achievements obtained by specific birds, as the birds of prey and other birds that have large air displacements. In other side, the man covers only the visible spectrum of light, of middle frequency, and does not see the ultraviolet light neither the infrared one, as other animals do it.
The sense of hearing permits to relate with the environment through the sonorous waves that travel through a flowed environment, for example the atmosphere or the water, pressuring these ambients. In a aquatic one, hearing is a more efficient organ than the view or the smell. This information travels in a slower velocity than in the light. Hearing has a medium development in the man. This it is not capable to hear sounds neither very weighty, case of whales, neither very sharp (ultrasounds) as do the bats. Besides his auditory sharpness (capacity to distinguish different sounds) and his auditory power (capacity to hear distant sounds) is moderate developed. The human species, being a visual animal, and in smaller stage a hearing animal, has the other senses less developed. The smell, the most primitive sense, is relatively weak, if we compare it with other mammals as the dogs, cats, ruminants, etc. The touch is the just one for a visual animal, although the man has corporal zones with a greater tactile development, due to the use. I refer to the face and specially to the hands. The taste also is discretely developed although is very versatile as corresponds to an omnivorous animal.
In conclusion, the human species has typical sensory organs of a diurnal, terrestrial animal, with ancestors of arboreus habits but they have passed to live in more open lands, like sabannah, and his intelligence has carried him to colonize all kinds of terrestial habitats.
9) Another tendency that is observed is a slow but gradual increment in the stature, perhaps as a result of an each time better diet.
Evolution as vertebrate animal
Besides, one must consider the evolution of the man in the context of the evolution of vertebrates.
A great evolutionary landmark was produced in the Devonien period, 370 m.y. (millions of years) ago, when populations of fish of lobely fins conquered the terrestrial environment and they were transformed into the first terrestrial vertebrates, the amphibians. Subsequently, in the Carboniferous, 300 m.y. ago, from populations of amphibians, appeared the first reptilians, that were diversified during the Mesozoic, originating, among others, the dinosaurs and reptilians like pterosaurs, that went the dominant terrestrial vertebrates of the mesozoic era.
The evolution of the dinosaurs deserves a comment aside. This group of reptiles is very special. It includes great variety of forms very diversified and adapted to practically all the terrestial habitats of the epoch. Its adaptive radiation can be compared with that of the mammals in the Cenozoic. They had more than 150 m.y. to evolve and to be diversified, so they arose at the beginning of the Triasic, 230 m.y. ago, and they were extinguished 65 m.y. ago, to ends of the Cretacic, as a result of the impact on the earth of a great asteroid. It is not to miss, therefore, the degree of complexity and adaptations that reached. Many carnivorous forms reached the homotermic bodies (the same as the birds and mammalian subsequent); as opposed to the remainder of the reptilians, the majority of the dinosaurs did not crawl, but they ambulated, that is, they raised the womb of the ground upon walking, so, they were provided of powerful extremities organized for such thing. Besides, many forms, especially the predators, reached a biped position, walking on the posterior extremities and being supported in their strong tail, leaving in liberty a weak anterior extremities, with powerful claws, that would be able to be utilized to attack to their prey, among others functions. These carnivorous and biped dinosaurs, as opposed to other, cuadruped and vegetarian, they should have a high metabolism and to be of quick movements, as the majority of the present mammals and birds. The visual capacity should be high, and is probable, that they could see colors, because it is believed they had covered with bright bodies colors, at least enough species. Many, had social habits; others, on the other hand, they were solitary. Some paleontogist believe that if the dinosaurs had not been extinguished, some of them, perhaps the biped forms, carnivorous and light, would have reached greater degree of intelligence.. Had they time to reach it anyone? Of light forms of carnivorous and biped dinosaurs, the fowls (birds)arose, in the end of the Triasic, 200 m.y. ago. These groups of dinosaurs were launched to the conquest of the air, therefore, the short previous extremities went transforming gradually in wings to fly and the posterior extremities were done thinner and light, being adapted to a bipedism characteristic of the fowls, in this one, more than walking, they jump, save the ostriches, that run. Also, its body was covered with protective and waterproof feathers and went himself doing gradually more small and light. The all body went himself adapting for more or less prolonged flights.
In the ends of the Permian, 250 m.y. ago, the therapsid arose, ambulate reptilian, and like the dinosaurs, they did not drag the womb upon walking; of these mammalian-reptilians arose, in the Triasic, the mammals. These one achieved a series of adaptations on terrestrial environment, more efficient than those of their predecessors the reptiles and analogous to those of the fowls, such as the homotermic bodies, the replacement of the scales of the skin by hairs, (feathers in the fowls) more efficient to obtain the homeoterm, and more protection for their breedings (placenta and milk food). The mesozoic mammalian were small and their life in the terrestrial environment should be hard, therefore they had to compete with the reptilian world that dominated the earth, especially with the dinosaurs. Is probable, they had nocturnal habits. With the extinction of the dinosaurs, in the cretacic-paleocene crisis, in the end of the Cretacic, the mammals took advantage of their opportunity and they occupied the empty habitats left by the extinct forms, having a adaptive radiation similar of the gigantic reptilians, during all the Cenozoic.
So, a relating to vertebrates, the terrestrial environment was dominated by the mammals, while the air environment was dominated by the fowls, the most next descendants of the dinosaurs. If we compare both evolutive diversifications, that of the dinosaurs in the Mesozoic and that of the mammals in the Cenozoic, we note that the first one elapsed along a a lot of more time than the second: 150 m.y. against 65 m. y. Nevertheless, the evolutive results of the diversification of the mammals have been more spectacular, that the one of the dinosaurs. The evolutive rhythm has accelerated in this second radiacción, of terrestrial vertebrates, and the resultant forms have been of smaller size although with similar adaptations. It is probable that, in these evolutive processes, geological and climatic changes have influenced: the climate has gone doing colder, the continents have gone separating, originating in the fragmentacion of the Pangea II, at the beginning of the Triasic, has happened the alpine orogeny, with its more intense phases in the Cenozoic and the consequent quaternary glaciation, in the final times of this orogeny. All these factors have determined the evolution of the alive animals, especially of the vertebrates that occupy us. Do not forget us that the dinosaurs evolved in a period, the Mesozoic, relatively stable since a climatic point of view, with humid and quite hot climates. Also we should keep in mind that the alive animals evolve more fast if are submitted to certain pressures of selection that oblige them to change and this is obtained for example when there are geographical, geological, and climatic changes that be it sufficiently important but not too much quick neither abrupt, therefore then the organism do not resist them and are extinguished.