Much of this fascinating article reminds me of Sex, Time, and Power: How Women's Sexuality Shaped Human Evolution, by Leonard Shalin, which probably was the book I most enjoyed reading last year, and from which I learned the most.
There's a lot in the book about humans' initial correlations of sex with the birth of a child nine months later, and with that connection, the ability to travel mentally into the future, and ultimately, to envisage mortality.
As this piece notes, optimism has evolved in part in an effort to counter what otherwise could prevent us from endeavoring to move the species forward, namely the awareness of our own inexorable deaths.
We like to think of ourselves as rational creatures. We watch our backs, weigh the odds, pack an umbrella. But both neuroscience and social science suggest that we are more optimistic than realistic. On average, we expect things to turn out better than they wind up being. […]
But the [optimism] bias also protects and inspires us: it keeps us moving forward rather than to the nearest high-rise ledge. Without optimism, our ancestors might never have ventured far from their tribes and we might all be cave dwellers, still huddled together and dreaming of light and heat. […]
Scientists who study memory proposed an intriguing answer [to the prevalence of brains creating false or wildly innacurate memories]: memories are susceptible to inaccuracies partly because the neural system responsible for remembering episodes from our past might not have evolved for memory alone. Rather, the core function of the memory system could in fact be to imagine the future -- to enable us to prepare for what has yet to come. The system is not designed to perfectly replay past events, the researchers claimed. It is designed to flexibly construct future scenarios in our minds. […]
It is easy to see why cognitive time travel was naturally selected for over the course of evolution. It allows us to plan ahead, to save food and resources for times of scarcity and to endure hard work in anticipation of a future reward. […]
I think the following also may apply to the more pessimistic among us. Ahem.
People with mild depression are relatively accurate when predicting future events. They see the world as it is. In other words, in the absence of a neural mechanism that generates unrealistic optimism, it is possible all humans would be mildly depressed.