Breathe airy biology again in underwater motion to time of greater part door for, nostril has self-evident interest in coping. Evolution comes as to how, drag in arrives length of bone of the upper jaw, neck position and position of nostril open one's mouth, concern how to go up directly pursue.
Human skull, the upper jaw is the shortest, door of head greater part is in vertebral and perpendicular position, neck can finite face upward, nostril is in the front.
Bovine skull, the upper jaw is in very long, nostril position leads to the upper jaw upper part. Because ox of time of greater part door lowers his head, in order to be time of door of nostril greater part gadarene. Swim when the ox, the neck can face upward to let the head and vertebral parallel, face upward time nostril has been in body coping, pose of buffalo natant time is very typical.
Original whale kind skull, the upper jaw is very long, the neck is firm to vertebral and parallel position, already fundamental shift went to nostril coping.
Finally, contemporary and cetacean, the head is farther outspread, can occupy body 1/3, neck nearly was done not have, the head is firm arrive with vertebral and parallel position, the open one's mouth of nostril is farther upgrade move.
In addition, cetacean nostril is not to be on the back, remain in the top of head. Look cetacean from appearance back and head were not showing boundary line, but be on skeleton by showing those who distinguish. Say to a form version is only on the back, after all the tool of popular science data is the mankind, person of greater part door mentions city of the top of head to think is vertebral and parallel outspread position, namely cetacean mouth whose person position, say nostril does not have a person to be able to be misunderstood on the back.