Afarensis is a 3.5-2.8 million year old hominin from the Kada Hadar member of the Hadar formation in the Middle Awash, Ethiopia. He is approximately 41 inches tall, weighs approximately 60 pounds and has a cranial capacity of a whopping 410 cc (approximately). Afarensis is currently considered to be transitional between apes and humans and displays some traits of both. Since he spends a lot of time on the couch watching monster movies, some observers question whether he is an obligate biped (although no one has observed him climbing a tree). He also has a blog called 
For the most part I have focused on talking about different species of primates. When I first came up with this series I also planned on doing some background posts that go into more detail on a specific subject within primatology. This is the first post along those lines. Because there is a lot of material to cover this will be broken into several posts. This post can be considered a general intoduction.
Primates are rather generalized mammals and in some instances retain primitive mammalian features - something that makes it hard to come up with a definitive diagnosis of the order. One feature, however, goes even further back.
Above is a picture of a deer foot. Notice it has four digits. Below is a rhino foot, it has three digits.
Most primates, however, retain the five digits of some of our early tetrapod ancestors.
While in other mammals the hands and feet became specialized for locomotion, in primates they also serve as a means of getting food. 
An extreme form of this can be seen in the hand of the aye-aye. The aye-aye eats burrowing insects and uses its index finger to hunt by tapping on a tree trunk and listening for echoes (a type of hunting called percussive hunting). When it finds an insect it uses the index finger to dig it out of the tree. One of the interesting things about this is that the finger can move completely independently of the others. The point here is that in primates the hands and feet are the result of a compromise between locomotion and food getting. Sometimes, as is the case with brachiators (explained more fully later in this series) locomotion wins, other times (as in the aye-aye) food wins. Adaptations for locomotion and food don't stop at the hands and feet. Such adaptations can also be seen in the limbs, pelvis, vertebrae and shoulder girdle. In future posts I will look at the different forms of locomotion displayed by primates and how they impact primate morphology. Ultimately, time and inclination permitting, I hope to take another look at the recent paper on orangutans and bipedalism
Comments
Cool post, but it looks to me like the long, skinny finger on the aye-aye hand is the middle finger, not the index.
Posted by: Nick | June 24, 2007 8:41 PM
That is due to the photo - the best I could find -the index finger of the aye-aye is definitely the longest.
Posted by: afarensis, FCD | June 24, 2007 11:01 PM