Well man has only explored about 0.4% of the earth. We're so fixated on finding new life on other planets that we seem to forget that we know very little about our own and there are creatures on this planet that have yet to be discovered.
Man has only been able to explore roughly about 5% of the ocean and that leaves a whooping 95% that we know nothing about. Taking into consideration the fact that the seven seas take up 70% of the earth you can see that we still have a long way to go.
In terms of land, there are places like Antarctica which are inhospitable to human beings and small islands like the Sentinel islands which are home to the sentinelese who are a violent people that attack any and every outsider that sets foot on their island. They're basically the last people on the planet untouched by civilization.
Then there's the Amazon rainforest which is over 2.5 miles of thick bush which is also yet to be explored completely. Not to mention the bottom of the oceans which are so deep that no human being could survive there.
There's still alot about this world that we don't know.
Do you have any references for this 0.4% claim?
Because, first the math doesns’t compute (5% of 70% is more than 0.4%), and additionally most of EurAsia and also Northern Americas is explored, with large parts of South America and Africa explored as well.
PS: NOAA.gov claims more than 80% of the oceans is unexplored, so that would point at 15% of 70%.
PPS: Many parts of the Amazon are explored already as well, but left alone because of the presence of tribes.