Well you know, bottom line, if you want to find intelligent life on Mars, put men up there! We put 12 men on the moon over a quarter of a century ago. Were would we be, in your opinion, if we had kept up that rate of exploration?
Well, I am not sure on this one. There were several directions we could have taken. One was the logical conclusion to the X-15 being an SSTO (Single Stage to Orbit) vehicle, or possibly a more defined presence in Earth's orbit. Would we have a greater presence on the Moon if we had continued? I am not sure.
Apollo was "pushed" to its very limits as a transport vehicle. I wish 18 and 19 flew, however, for a long term “residence” a different (heavy lifting) spacecraft would have been required. A Mission to Mars is such a huge endeavor compared to the Moon that I believe it would still be in the wings even if the space program had not been cut back. Earth orbit and lunar resources should be the priority for the moment.