Does Psalms 90:10 say that the lifespan of humans is 70-80 years?
The verse you quoted from Psalm 90 must be understood in its context (as is the case with all scripture). The context of v.10 is:
Notice the Psalmist’s line of thought in this passage. He is speaking on behalf of the nation of Israel (i.e., “we”). The people of Israel were under God’s judgment for their disobedience under the Old Covenant. God was “consuming” Israel in His fury and anger against them. Israel endured exile, bondage, drought, famine and other consequences for their apostasy to the covenant.
In v.8 the Psalmist says Israel sins were “before” God. Though Israel thought they were sinning in secret, the Psalmist says their secret sins were placed in the light of God’s presence. In other words, they weren’t so secret after all. Because of Israel’s unrepentant sins, the Old consumed His people in fury through judgments that weakened them and brought them to early death.
In v.10 the psalmist says the life of a person is seventy or maybe eighty years, yet the pride of our years is merely labor and sorrow. No matter how long we may live, soon we are gone in the end. Therefore, the psalmist asks God to teach His people to number their days, which means to appreciate the fragile and fleeting nature of life on earth. By gaining a healthy appreciation for our mortality, God’s people would live with wisdom for whatever time the Lord gives.
Therefore in this context, it’s clear the psalmist is not specifying an exact length of life for all human beings. Rather, he’s remarking in a general way that most people live between 70-80 years, which is still true today. Some may live fewer years and some may live longer. Nevertheless, 70-80 years is generally the length of life for mankind, and in eternal terms, it’s a very short time indeed. Therefore, we must live with an appreciation for the eternal consequences of how we live.