The short answer to this question is "there is no way to even guess", the long answer involves explaining why, so here we go!

Lets start with the past 100 years. For simplicity's sake lets just assume that everyone who was alive in 1900 is now dead because that is pretty much true. That's about 1 billion people. Now most people who were born since then are also dead so lets take 80% of the population in 1950 and add that, that's 2.5 billion.

So we now have 3.5 billion dead people but what languages did they speak? This is hard to figure out but lets just base it off geography. North america has around 254 million dead people right now so we'll just say they all speak English. Now I wanna add the UK. The wikipedia page goes back to 1960 so I'm just going to use that number which is about 52 million but a lot of people who were alive in 1960 are still alive so I'm gonna say 75% of them are dead now so add 39 million. Now we have 293 million dead English speakers.

Based off the same data (here) there are basically 2 billion dead people from Asia and they all spoke a huge number of different languages. So right now you may be thinking "Holy shit, thatss a lot of definite data, and we know what languages these people would have been speaking!" Well not so fast Mr. Conclusions.

Lets now consider everyone that died before the modern era because for most of them there isn't really anyway to know what they were speaking. Sure we kind of know ancient Egyptian, Hebrew and some other documented cultures but for ever documented culture there are many more undocumented cultures and languages. According to the Population Reference Bureau about 107 billion people have ever lived. 7 billion of them are alive today. We already know that 293 million of them spoke English. We can also more or less figure out what people have spoken in the 20th century so we can exclude them so thats minus 4 billion people or so. We are left with 96 billion people who lived before the 20th century. We do know what many of those people spoke though so lets just chop off another 6 billion people there just to safe but I doubt the number is really that high. This leaves us with 90 billion people for whom we have no idea what language they would have spoken. There is simply no evidence, no way of ever reconstructing it or hearing it, it is simply gone.

TL;DR: So there you go, for the vast majority of people that ever lived we have no idea what languages they spoke and we will never know. 90 billion lived and died and we'll never know a single word they ever uttered.

This is a difficult, and perhaps impossible, question to answer. We simply don't know what languages anatomically modern humans were speaking for most of their anatomical modernity, though perhaps their number is so small as to not matter. Once we get to time-depths where we have a better idea of what people were speaking, we're faced with the eternally thorny question of what a "language" is. How do we decide whether someone is speaking Middle English or Early Modern? And how do we justify this, given that the two varieties necessarily shade together almost imperceptibly? And if we accept that Middle and Early Modern English form a continuum, what about their continuum with Old English, and the continuum of that with Proto-Germanic, and of that with pre-Germanic, and of that with late northwestern dialects of Proto-Indo-European, and of that with somewhat earlier dialects of Proto-Indo-European? And having established this continuum, what about the connected continuum of early dialects of PIE with later dialects ancestral to, say, Baltic and Slavic, and so forth to these other modern languages.

I don't mean to say that we can't meaningfully distinguish between Russian, Old Church Slavonic, English, Gothic, and the speech of speakers at different points in time, but we have to recognize that there is a very real continuity between lots of modern languages, and we need to be prepared to brook a certain amount of arbitrariness to answer a question like this.