Many essential non-renewable resources are expected to run out within the next 100 years. Have we, the humans, a species in our infancy, gambled away our future? Most of these resources we used for our petty pleasures. Today oil is on average equivalent to 150 slaves to each person alive. Helium, oil, rare minerals and many other non-renewable resources are running out. It is conceivable that these materials might have played an important role in science and perhaps even saved the human species one day from extinction by making devices such as warp drive possible.
The fundamental problem of mankind is their inability to understand the exponential function. The only sustainable condition for mankind to exist is zero growth in balance with renewable resources (or at least growth must decay or follow a pattern which satisfies this balance). Energy consumed must not exceed energy arriving on this planet. Most of the energy available on this planet originates from the sun (excluding nuclear and geothermal), and their availability is always finite. The surface area of the planet is finite, output of the ecosystem is finite, mankind already consumes over 40% of the output of photosynthesis. The efficiency of our production can at best only approach 100%. For the population to reach an equilibrium the number of people born must equal the number of people dying. Growing life expectancies must be accompanied by declining birth rates. The total number of people on this planet are already near the limit of the carrying capacity of this planet. At the moment, by maintaining our current lifestyle, we are borrowing from the future generations. Perhaps we should know better.
The energy crisis and overpopulation is not even a technological problem, it is an economic and political one. The inflationary banking system forces exponential growth and cannot in its current form properly function without it.
It is ironic that improving the efficiency by which a resource is used tends to increase (rather than decrease) the rate of consumption of that resource. In 1865, the English economist William Stanley Jevons argued that, contrary to intuition, technological improvements could not be relied upon to reduce consumption.
Some people refuse to understand the simple math behind exponential growth. No matter how low a growth rate, an exponential growth if allowed to continue, will eventually hit some sort of physical limit, if nothing else then it will be limited by the speed of light. If human population keeps growing, the sphere containing the combined volume of their bodies will eventually need to grow at a speed faster than the speed of light. Now one doesn't needs to be a genius to understand why this is impossible.
Another interesting prospect has to do with curing death and disease which I would argue is a simple engineering problem compared to fundamental problems of energy, time and space. Human by our best knowledge is a finite machine with finite complexity and all such machines can be fixed. The human DNA can be stored on a single DVD (or in fact much less), that is how little information is contained in the human blueprint. Crabs and lobsters have an unusual longevity for arthropods, their mortality rate does not increase with age, and this is attributed to DNA repair by the enzyme telomerase, in effect, they do not die of old age. Considering the advances in genetic engineering it is perfectly conceivable that we might eventually cure death by old age. Under such conditions we would be forced to decide between living forever or having children. Children could only be had as a replacement of existing people. Perhaps having been passed away due to accidents or perhaps by trading one life for another. It would become a rare gift or a lucky chance to be given a right to have a child. It is my opinion that having children should already be regulated and people wishing to become parents should go through exams to guarantee at least a minimal level of competence for the task of bringing up a child, but perhaps that's another story for another time.
What we will eventually need to do though, is to choose to live a life of less consumption than what we are short-term capable. A life in which consumption is planned for an infinite timespan and sustainable existence. We need to minimize the total suffering of all living beings while maximizing the sum of happiness for those alive. Those who were never born cannot suffer. I don't think the human species should become extinct, but it should be stabilized at a level which is in par with the natural renewal rate of the resources. This level of population is probably much less than the current level of people, possible by more than factor of 10. Perhaps something like 500 million people would be a better number.
Perhaps the reason why aliens have never visited us is because throughout the universe, no civilization can ever progress much beyond our current level because they simply exhaust their resources and stop advancing before technology would make it possible for them to leave their solar system. Though in the long run, this should not be a problem since one should be able achieve a balance with energy we get from the sun. Perhaps mankind or the universe is just not old enough yet.