1976 in Tanzania, a team led by paleontologist Mary Leakey found sets of fossilized footprints that looked as if they could of been left by humans. The footprints were clearly of a bipedal creature but the problem was that these fossilized footprints were 3.6 million years old !

This was the first time in our history that scientists found evidence of bipedalism (the ability to walk to 2 feet as we do) in an early hominid creature. Up till then, the behavior of early creatures always had to be inferred from the evidence of bones and teeth. But not this time, this time there was fossilized evidence of "behavior"! (pbs.org, 2001)

These fossilized footprints represent a drop in the bucket of the fossil evidence that shows human evolution. Earlier that decade in 1974, a skeleton was found of a creature we name Australopithecus Afarensis. This creatures skeleon was different from other primates because the knees could "lock into place", the femur was slanted inward, and the large toe was in line with the rest of the toes on the foot. These simple attributes allow bipedalism as a primary mode of locomotion! Although this was evidence of a bipedal primate that lived millions of years ago, the brain size (as dictated by skull capacity) was relatively small (about the size of a chimp).

Being bipedal is a huge advantageous adaption for humans. Some of the advantages of being bipedal include:

the ability to run and carry food at the same time

the ability to travel longer distances

having hands free for tool use

an ability to have a better field of vision (see further).

The next major adaptation that appeared later during the course of "human evolution" was an increase in brain size. The fossils allow us to see how brain size has increased over the last 3 to 4 million years. Early "hominids" or (human like primates) had chimp size brains that are approximately 450cc.

Another early hominid which appeared after Australopithecus had a brain that was 650cc. This increase in brain size allowed this creature named "homo habilis" to develop and use tools. The take away message from this is that as brain size increased, new capabilities evolved! An increase in brain size and "evolution of capabilities" allowed early primates like this to modify their environment to suit their needs!

Later down the timeline we now have "Homo Erectus"with a brain size of 900cc. This creature was the 1st to develop what we would consider, a "human like" culture.(discovery.com, 2001) This creature:

used tools

made fire

spread out of Africa into Asia.

Modern humans have brains that are approximately 1200cc and have even more sophisticated capabilities that are not only due to brain size, but due to neurological developments within the brain itself!

Interestingly, we know that brain size isnt all its cracked up to be. Another hominid named Homo Neanderthalensis had a brain of 1300cc. Yes, larger than our current brains relatively. Yet was still much less sophisticated than humans and was possibly made extinct by humans!

Out story of our recent ancestry begins in Africa where humans were once a minor species and migrated to fill all of the continents. This migration is dictated by the evidence obtained in fossils and even better by molecular and genetic evidence! Mitochondrial DNA is being studied in modern science and it shows us that Neanderthals and modern humans although they were alive at the same time, did not interbreed.

Science is an ongoing process of progress. In evolution, as with any scientific and logical discipline, new evidence will continually emerge and will continually require re-examination!