Final answer:
The evolution of long necks in male giraffes, which aids in both fighting and feeding, is a result of sexual selection and natural selection, leading to greater fitness.
Step-by-step explanation:
Male giraffes with longer necks tend to win more fights and have greater access to mating opportunities. This results in the evolution of long necks through a process known as sexual selection. In the case of giraffes, these longer necks also provide an advantage in feeding, as they allow these animals to reach leaves.
This natural advantage contributes to the overall fitness of long-necked giraffes, as they have a better chance of surviving and reproducing. Over generations, this results in the trait of long necks becoming more common within the giraffe population.
Unlike Lamarck's theory, which proposed that acquired traits such as a longer neck would be directly passed on to offspring, it is now understood through natural selection that giraffes with genetically longer necks have a higher likelihood of surviving and passing on their genes.