Biological speaking a sentient species (humanity) would be deemed a failed species by the law of nature if we do not evolve into what is called "transcendence" a state in which we shave off our physical bodies and turn our conciseness into pure energy which can be neither created nor destroyed thus escaping death this could however take a few million years.
Getting into aliens (if you believe) they're always depicted with small bodies and huge heads this means there much closer to the state of transcendence then humanity is, meaning they have been around a lot longer than us, as they no longer need strong durable physical bodies to help them survive
Current research into immorality is being done in Russia were they are trying to save a conciseness (the you personality and all) and store it into a machine by which you could then be uploaded into another cloned body so in theory you could live forever only needing to change your body every half a century or so.
No matter what medical advances we make our bodies aren't built to sustain an infinite life expectancy, pathogens will always evolve with science besides if immortality led to a bad quality of life eg permanent care needs, risky operations that could cause health problems and dependency on life support systems would that really be conquering death or just dying in a different way? What we can do is reduce the frequency of early unnecessary deaths. Also with our natural resource shortage and overpopulation crisis keeping people alive for too long could contribute to worse suffering for humanity in later years.
Death is inevitable. Death will surely come. Death is scared of none. Ashes to ashes and dust to dust. Your rotting bodies will fall to rust. I particularly like this topic because it is quite humorous to debate on a subject that is inevitable. Even if immortality was a possibility, I asure you that you would wish you could die. Never ending life would get boring and painful after a while.