Updated: Jun 9
How ancestral migration chains impact today's decision-making
About the graphic: This graphic shows two examples of ancestral migration chains. These 2 example ancestral chain paths show 1) an East Africa through West Africa to America ancestral chain and 2) an East Africa through the Middle East through Europe to Americal ancestral chain. Please do not feel left out if you do not see your favorite geography! Only 2 chains were chosen to simplify the map. There are around 8 billion paths from those alive today available to choose from.
Each chain has two commonalities:
All human ancestry originates in East Africa.
All current humans evolved from humans with the strong presence of “fight or flight” decision-making DNA. All individuals today are at the end of a 400-person ancestral chain. By definition, all of our ancestors were very good at “running from the lion!”
Our ancient, fight-or-flight-based decision-making ability is challenged by today's more common complex decisions. Personal finance and personal health involve important life decisions impacting long-term success. Personal finance and personal health share the reality that long-term success occurs decades after high-impact decisions needed to be made. [iii] These are particularly complex because they involve time trade-offs. Time trade-offs include the give-up-a-little now to earn a significant pay-off in the future decisions. People lack the natural capacity to handle time uncertainty.
Our neurobiology, as a result of evolutionary biology fine-tuning, makes us naturally very present-focused. If you think about it, for tens of thousands of years, your ancestors stayed alive long enough to have a family by successfully answering and activating super important, life-sustaining questions like: "Should I run from this lion?" Thus, that present-focused "fight or flight" decision-making got wired into our brains. The fact that you are reading this means that your entire line of ancestors successfully ran from the lion!
Our hard-wired fight or flight decision-making processes have subtle and significant impacts on our day-to-day decision-making. Related to the graphic, good follow-up questions to understand the importance and impact of our subconscious decision-making routines are:
How many generations came before me? and
What is the probability that I am here today as a product of all my ancestors?
Adam Frank is an astrophysics professor at the University of Rochester. Dr. Frank estimates there have been 400 human generations between now and the beginning of humanity. [i] While your ancestral tree branched off from the first human generation, we all have about 400 generations. Now let's do some quick math. In the case of generational math, probabilistic combinations are serially dependent. This means, for you to be alive today, every preceding generation had to live long enough to have children. If there was one break in the chain, you would not exist! The formula for the dependent serial combination is:
The chance of you being alive today = P^N
P is the average probability of all generations living long enough to have children and
N is the number of generations.
So, very conservatively, we estimate there is a 90% average chance since the beginning of time that each of your ancestors lived long enough to have the next child in your generational chain. Since there are 400 generations, the probability you or any of us are here today is an astoundingly low probability approaching 0 (.9^400 equals a super small number with 19 zeros to the right of the decimal point!)
That means you are exceedingly rare. Your existence is a probabilistic rounding error. No wonder your genetic decision-making code has been hard-wired for fast fight-or-flight decisions. It was the precious few people that escaped from the lion to have children! The vast majority of "lion snack peeps" did not live long enough to pass on their slower decision-making DNA. The resulting human genetic focus on fight-or-flight decision-making demonstrates the compound fine-tuning power of natural selection.
Today, unless there is a jailbreak at the local zoo, we rarely make these sorts of very important but simple binary decisions. In fact, modern laws and medicine have virtually eliminated short-term existential threats. The vast majority of modern people can safely live until they are old enough to have children. However, that ancient decision-making wiring is still present in our DNA. We are naturally very good at making mostly unnecessary-for-our-modern-world decisions.
On the flip side, our brains are NOT wired to intuitively make today's necessary complex, multi-criteria, multi-alternative decisions. Without assistance, this may lead to poor decision outcomes. In fact, because our brains are naturally wired to make fast, life-saving decisions, that wiring often works against the slower evaluation process needed for making complex, multi-criteria, multi-alternative decisions. The difference between ancient brain decisions we are naturally good at and modern, difficult complex decisions present as cognitive biases. Our cognitive biases hinder us from properly saving for retirement or from keeping healthy New Year's resolutions. [ii] It is our evolutionary biology working against us!
For a deeper dive and helpful references, please see our article:
[i] Frank, Who Were Your Millionth-Great-Grandparents? National Public Radio, 2017
To be fair, the exact date and generation number of when humanity started may never be exactly known. That is not the way evolution works. What constitutes a "first human" is not an answerable question. The slow, genetic mutation, and natural selection process only provide incremental changes from generation to generation. Thus, the current human form is an ongoing variation that started at the beginning of biological life. In this article, assigning 400 generations as theorized by Dr. Frank is a helpful anchoring point to demonstrate the degree to which human life is such a rare event. Before modern times, the vast, vast majority of people born did not make it to childbearing age. This fact demonstrates the power of our ancient, "Fight or Flight" decision wiring as a means to pass on our genetic code.
[ii] Hulett, Solving the Decision-making Crisis: Making the most of our free will, The Curiosity Vine, 2023