#口语喵第 17 期 Day 4#
progress in which animals' behavior that originally had practical purpose developed into one that communicate specific message
1： before biting, dogs bared their teeth to avoid bite their lips
2: animals get to know this means the dog is ready to attack
3:Dogs realized teeth baring can make other animals back off without attacking.
4 At last dogs started using it as a warning signal.
therefore, if an animal engages in this behavior, other animals will be able to interpret the meaning o the behavior quickly and respond appropriately