Weight/mass of mars in metric tons: 6.39 × 10^20 t Average weight of 1 adult human: 70 kilos (1,000 kilos for 1 ton) Thats 14 people for 1 metric ton: Weight/mass of mars: 639,000,000,000,000,000,000 metric tons Thats: 4,500,000,000,000,000,000 adult humans (450,000x 1 trillion exactly) So no the weight of ALL human life forms in ONE galaxy (if each world holds a trillion thats 450,000 of them roughly) IS Barely equal to the weight of mars! (My original guess was 100,000x a trillion, you need 4.5x that JUST to get close to mass of mars and mars is a SMALL planet! Thats also FULL body weight not just nervous system)