Comprehending Deep Time
Last year an important study on great ape generation length effectively doubled the amount of time since our divergence with chimpanzees and bonobos. Many evolutionary anthropologists now believe that the human-chimp-bonobo divergence occurred between 7-14 million years ago, as opposed to 6 million years ago (the larger range is the product of speciation being a long-term process, as opposed to immediate). And earlier this year the European Space Agency announced new data indicating our universe is 50 million years older than previously believed (from 13.77 to 13.82 billion years old). Both of these studies force us to reconceptualize our reality: the first challenges our interpretation of human evolution, and the second challenges our interpretation of the universe’s history and development.
But how can we best understand these numbers and reinterpretations?
Attempting to comprehend the unimaginably long stretch of time that preceded the present is something many scientists must confront. This usually poses incredible challenges because our minds have evolved to conceptualize time on scales of years, decades, and centuries; as opposed to time on scales of millions or billions of years. In fact, even conceptualizing the timescales of human civilization is quite daunting. For example, Ancient Egyptian civilization lasted from 3,000 B.C.E. to 332 B.C.E., which for context is 13 times longer than independent United States history.
Evolutionary biologist and paleontologist Stephen J. Gould dedicated his life to understand phenomenon on deep time scales. He stated that:
The human mind may not have evolved enough to be able to comprehend deep time. It may only be able to measure it. An abstract, intellectual understanding of deep time comes easily enough, getting it into the gut is quite another matter.
I understand (and respect) Gould’s opinion on this issue, but I slightly disagree. I do not think that an abstract, intellectual understanding of deep time comes easily. When I was in college I spent hours thinking hard about deep time. In order to improve my understanding of phenomena on these time scales I frequently relied on metaphor and varying time scale comparisons. I also read books about the history of the universe that detailed events in reverse chronology. I felt as though reverse chronology accounts of our past eased me gently into ever greater time scales. Once I had absorbed an understanding of phenomena that occurred on scales of millennia, it was far easier for me to absorb an understanding of phenomena that occurred on scales of hundreds of millennia. After applying this approach, it became progressively easier to view all events in our contemporary world from the perspective of cosmic time.
Applying this approach also helps to understand studies that alter the master narrative of existence like the two papers mentioned above. How should we approach an understanding of the new human-chimpanzee-bonobo divergence time and the new age of our universe? I would argue that for proper context we should consult one of the most important intellectual tools humans have developed to understand deep time: the Cosmic Calendar.
Astronomer Carl Sagan popularized the Cosmic Calendar in the 1980s. This calendar is used to map the entire lifetime of the universe, and all significant events, onto a single calendar year. By employing this calendar metaphor, the human mind is able to approach un-human time scales in a human format.
For the recalculated human-chimpanzee-bonobo divergence time we must now conceptualize a gradual split that occurred over a scale of 7 million years (14-7mya), as opposed to a relatively sudden split 6 mya. A speciation occurring over 7 million years is almost an unfathomably long period of time. Once modern humans had left Africa it took them ~50,000 years to colonize nearly every available landmass on the planet. That means the human-chimpanzee-bonobo speciation event took 140 times longer than human colonization of the entire planet!
On the Cosmic Calendar our previous understanding of the human-chimpanzee-bonobo speciation event occurred on December 31st at approximately 20:04 P.M. So with this framework the critical split leading to the evolution of humans occurred about 4 hours before the New Year! Under our new interpretation we can still imagine the split as occurring on December 31st. However, the key difference is that the split will be occurring over several hours: from 15:24-19:04 P.M. So the human emergence story is now occupying a slightly larger fraction of the famous Cosmic Calendar.
But let’s remember to put this in proper perspective. Biological evolution, and speciation specifically, can take millions of years. For the human mind this is nearly impossible to understand without a useful tool like a Cosmic Calendar. As I stated above, the speciation event between humans and our closest relatives took 140 times longer than the complete colonization of the planet. Yet we still only emerge on the last day of the universe’s time scale. Our distant hominid ancestors made it just in time for the New Year’s Party.
The universe’s age was also recalculated last week. For many people this may not mean very much. What is the difference between 13.77 and 13.82? This may seem like an inconsequential age extension of a universe we already knew was ancient. But let’s remember that 13.77 BILLION to 13.82 BILLION (~50 million years) is the difference between primates and no primates. Almost all of primate evolution, and certainly all-significant events within primate evolution, occurred within the last 50 million years! Approximately 50 million years ago, lemurs had yet to raft to Madagascar, New World Monkeys had yet to make their mysterious journey to South America, and apes did not exist at all!
The reason I discussed time scales related to great ape evolution (e.g., hundreds of thousands of years and millions of years) first was to ease you back into the world of billions. On the Cosmic Calendar the reimagining of a universe 50 million years older does not change very much: our galaxy still forms around the same time, as does our planet, and life, and all other significant developments in the history of our universe. This is because on the scale of the universe, 50 million years is comparable to a couple of months for a human. The equivalent of adding all of primate evolution to the Cosmic Calendar is inconsequential to the unimaginable expanse of cosmic time.
Why is this important to understand? Apart from being mind-bendingly cool and being a useful tool to help you understand scientific discoveries; it should also help you put your own life in context. Our entire order’s evolution is nothing on the temporal scale of billions of years. Our species emergence is but a preamble to the universe’s New Year’s Eve party. And modern civilization? We arrived a few seconds (13 seconds to be fair), before the ball dropped. When we start to discuss an individual’s life, we may be diving into the temporal scales of nanoseconds.
If those scales do not humble you, nothing will.
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