In my thoughts, I would say the ability to form a working civilization, and keep it going. Second to that, Language. (And soon, Technology. While already a great achievement, improvements and advances will be made to make it even better, and eventually one of the greatest achievements)
The alphabet/writing without doubt. Fire was a discovery not an achievement, others have said language but this is not unique to humans, and nothing else mentioned would have been possible without the means with which to record and share information. Now of course the only thing that separates us from other animals is abstract thought, and without it we would not have the alphabet, but that was a construct of evolution and not an achievement initiated by humankind.
The alphabet and writing. Without it, everything would still be word of mouth..... ~ " My friend told me the earth was flat. " " It must be true then. Let me tell my friends. " ~ ~ The internet and technology would not be possible without the written word. All living things have "language" and "working civilizations" of some sort.
9 months ago
Last edited at 9:40AM on 3/20/2013
I tend to agree with the two Angels above. Nothing has done more to give us the potential to finally become one, interconnected, worldwide community, and all the benefits that can come from such a relationship. Interestingly, in 2011 the United Nations declared the Internet to be a fundamental human right.