When was the last time you paused to ponder about:

– Why am I here?

– How did I inherit my looks?

– What is the origin of the genes that define me and my existence? If we trace these genes back far enough, do we uncover peculiarities that would require quirky illustrations to explain?

To unravel this journey, let’s begin in the present and backtrack, tracing our genetic heritage at significant junctures.

Let’s start with you. While I don’t know you, odds are, you resemble this:

For simplicity, let’s focus on your patriline, the lineage through your male relatives.

So, taking a step back, we encounter your father:

Next, we arrive at your grandfather, great grandfather, and eventually, your great great-grandfather, born around 1825-1875. This is how he looked:

Your great-great-grandfather lived in a time without amenities like running water or electricity, likely holding more archaic views. While you never met him, your existence is tied to his.

Now, let’s move to his ancestors—going back 18 generations to your [great x 20] grandfather:

Your great²⁰ grandfather faced a harsh reality. Amidst turmoil and wars, he lived through challenging times. Imagine his surprise if he could observe your comparatively easy life. Yet, your great⁵⁰⁰ grandfather would be even more amazed.

Your great⁵⁰⁰ grandfather led a primal existence, focused on survival and procreation. His actions, though basic, were crucial for your lineage’s continuation and the emergence of millions like you today.

Looming further back, we encounter a time predating modern humans—an era inhabited by a notable figure known as Y-chromosomal Adam. He is recognized as the most recent common male ancestor of all living humans, transcending as the common forefather of humanity.

Y-chromosomal Adam, although a questionable character in history, played a pivotal role in passing down his genetic legacy, contributing to the existence of all present-day individuals. Without him, life would have unfolded distinctly, and none of us would be here today.

Transitioning into the unusual, 3 million years ago, our ancestors embodied a hybrid form called Australopithecus. Your great^220,000 grandfather, although primitive by our standards, marked a pivotal shift as one of the earliest bipeds, propelling human evolution towards intelligence and innovation.

As we delve deeper, your great^550,000 grandfather emerges as a significant primate ancestor, branching off to form the lineage of both humans and chimpanzees. This marked a crucial evolutionary divergence around 6 million years ago, shaping the distinct paths of human and chimpanzee evolution.

In a departure from his descendants, your great^15,000,000 grandfather coexisted with dinosaurs. Serving as a common ancestor to modern primates, he navigated a world teeming with prehistoric giants, laying down the genetic blueprint for future primate evolution.

Take a moment to fathom that your great^55,000,000 grandfather embodied a humble rodent. Considered the first placental mammal, he birthed the lineage of all non-marsupial mammals. Thus, if whales could recount their lineage, they would find themselves embracing a shared genetic history until this point—aligned with your own.

Your great^125m grandfather, an early lizard, paved the way for modern vertebrate evolution. Equipped with rudimentary limbs and an advanced nervous system, he marked the divergence point between mammals, reptiles, and birds, laying the foundation for diverse ancestral paths.

Your great^160m grandfather, a fish making forays onto land, pioneered the transition from aquatic to terrestrial life forms. His evolutionary journey heralded critical adaptations such as limb formation and the development of primitive lungs—a crucial shift that set the stage for future vertebrate evolution.

Termed an Acanthostega, his innovative traits laid the groundwork for subsequent species’ anatomical advancements.

Taking a leap back to your great^220m grandfather, we find a fish as your forebearer. Remarkably, evolution sculpted his fins into the limbs we use today. Noteworthy for being the first vertebrate with a jaw, he heralded a significant physiological innovation that steered life towards present-day anatomical configurations.

Your great^255m grandfather, resembling a flatworm, played a key role in evolutionary history, being the earliest bilateral organism with brain functionality. His legacy encompasses fundamental developments like neural structures and rudimentary body symmetry.

Your lineage also embraces a jellyfish ancestor, marking a significant epoch where nerves, muscles, and basic sensory organs emerged. This era, with the advent of complex sensory systems, paved the way for diverse life forms to evolve and thrive.

Reflect on the vast tapestry of your genetic history:

1) The Richness of Your Genetic Story: Your genetic makeup is a culmination of trillions of interconnected organisms and countless optimal mutations over eons. Every aspect of your being bears the imprints of past creatures like the jellyfish, lizard, and monkey, adapting through millions of years of existence.

Every action or reaction you display today echoes the intertwined legacy you share with these diverse species, manifesting in your intricate biological makeup.

2) The Remarkable Unlikelihood of Your Existence: Considering the extensive chain of ancestors leading to your birth, spanning over a trillion forebears, each life lost in this continuum would have altered the course of evolution, possibly resulting in a world devoid of your unique presence. Your existence, in all its intricacies, stands as a testament to the extraordinary odds that shaped your being.

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If you enjoyed this piece, explore these topics next:

Your Family: Past, Present, and Future – Exploring the intricacies of familial lineages

Horizontal History – Examining history from a unique perspective

The Primate Awards – Unveiling the untold stories of your primate ancestors

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The estimates were based on average generation lengths derived from the lifespan and reproductive ages of various species in the ancestral line. The approximations ranged from 25 years for humans to one day for single-cell organisms.

Sources
– Toth, Nicholas and Schick, Kathy (2005). “African Origins” in The Human Past: World Prehistory and the Development of Human Societies (Editor: Chris Scarre). London: Thames and Hudson. Page 60.
– Richard Dawkins 2004 The Ancestor’s Tale page 136, 250, and 289.
– A Jurassic eutherian mammal and divergence of marsupials and placentals http://dx.doi.org/10.1038/nature10291
– Eckhart L, Valle LD, Jaeger K, et al. (November 2008). Proceedings of the National Academy of Sciences of the United States of America 105 (47): 18419–23.
– http://web.archive.org/web/20090319201312/http://www.uhh.hawaii.edu/~ronald/392/Homol-Gill-Jaw.JPG
– http://www.ucmp.berkeley.edu/protista/proterospongia.html
– Numerous references from Wikipedia were used in research.

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