I do not think we were "designed" to live in the 21st century. A lot of people love life now and couldn't imagine going back to our prehistoric ways, but we have issues now. Depression, anxiety, sleeping issues. Our adrenal glands are huge, and this causes us to lose our minds in the most ridiculous of places--like a traffic jam.
People in southern India live different than they do in Alaska or china. An inhabitant of Germany would have a different life style from most Brazilians. The fact that this question was not specified gives me some leverage. In most parts of the US, one does not need to have a very strong body. However, this is made up by the fact that there is a huge emphasis on sports, so our muscles are not outdated, and are definitely capable of dealing with 21st century life. In many cultures, especially in sub-Saharan Africa, people gain respect based on how many children they can produce, and so our current reproductive organs are not outdated either. The over consumption of alcohol in several western and Slavic cultures means our livers are not outdated, although they are being pushed to their limits. The list could go on forever. The human body has prevailed in all environments on the earth, even better than all previous hominids. I do not think our bodies are adapting to the different aspects of their societies, i think society is adapting to the different parts of the human body that need to be taken into consideration.
No, our bodies are not outdated and incapable of dealing with 21st century life. Our bodies are continually changing in small ways all the time. Just as we likely would not be able to deal with 17th century life, it's unlikely that someone from that era could deal with our time.
I would argue that our bodies are not outdated but that we are not supposed to be living life the way we do in the 21st century. What I mean by this is that we spend a large amount of our days infront of computer sitting. I believe our bodies were made for moving and exploring. Yes out bodies are incapable of dealing with 21st century life but they are not outdated.
And evolve over time, so that we are able to make due with out bodies and the environment around us that sometimes gives us challenges and forces our bodies to change over time. I think that the challenges that we face as the human race in the 21st century does not have to do very much with how are bodies are in the 21st century for the most part really though.
No, I am very fit, and work hard all the time to make sure my body is in a good condition, and can handle anything that this world throws at me. So I think I am capable of dealing with life in the twenty first century, and I think most are.