The human brain has been evolving since the dawn of time, when we were all single cell organisms, Darwin's Theory of Evolution states that we all evolved from these common beings, but all living things on Earth evolved in different ways (obviously or everything would be exactly the same). So lets move forward a little to about 13,000,000 years ago this is when our distant distant (add the word distant many more times) relative Pierolapithecus Catalaunicus first began to show signs of greater intelligence and sociability. Now lets jump ahead to a slightly less distant relative the Australopithecus afarensis, also known as the famous Lucy fossil, at this point we still had brains relatively similar in size to our cousins the chimpanzees and gorillas. However during this evolutionary period our brains started to show some changes in structure and shape, one example of this was that our neocortex began to expand and reorganize certain functions. Since this time, beginning with the appearance of Homo habilis the first of our genus, our brain's size and capabilities have continued to expand. Roughly 1.9 million years ago we saw an expansion in brain size, including an expansion of the now known as Broca's Area which is directly related to speech and its comprehension. Early Homo erectus fossils from about 1.8 million years ago showed brain sizes of about 600ml, and from there we showed continued increases in brain size and power. In fact the biggest changes in our brain have come relatively recently in our evolutionary history as can be seen in the image to the right. We can see the increases in intelligence as well, as our ancestors began to develop more complex tools, and more intricate rituals. By 500,000 years ago our brains had grown to over 1000ml, close to todays average of over 1200ml's. However, it is not just brain size that gives us the ability to reason, and problem solve, but the complexity of our brain as well. Compared to a chimpanzee humans have far more white matter in the temporal cortex which represents more connections between nerve cells which gives us a greater ability to process information. In relation to our size our brains are far larger than other mammals, as well as more complex. This along with to evolution of our affinity for collective learning, which means we can take the teachings of one generation and improve upon it with the next, is what has allowed us to move from hunter gathers, to the civilizations that we are today. However, just like with that cultural and societal evolution there are always pros and cons. This is also true for our development of larger brains, For example, we can store information, collect and process information, solve problems, and ponder abstract ideas to name a few of the pro's, but it also uses up great deal of our bodies energy, oxygen, and blood flow, and created difficulty when it comes to childbirth. It is the brain's high energy usage that has led some to theorize that it was our development of using fire to cook meat that contributed to the brains rapid increase in size, as we now had a way to increase our body's energy intake. Our understanding of human evolution is itself always evolving, to understand this we just need to look at the discovery, that began in 2013 and was announced in 2015, of a new ancestor in our evolutionary tree. Fossils of the Homo naledi has raised new questions about our evolutionary journey. Found in a cave in South Africa these new fossils also raise new questions about how our brains developed. While they have a body similar in size to Homo erectus, their brain's were about the size of an orange, much smaller than you would expect to see. According to the anthropologists who worked on the discovery Homo naledi was a mix of primitive and more modern hominin traits.