- Have you ever contemplated about the origins of life on this planet? If so, you probably have familiarized yourself with many of the ancient creatures that inhabited our world long ago. You might also know that life first originated in the sea well before making the transition to land.
In fact, the sea was the only sanctuary for life for billions of years until about 430 million years ago (Scientific American). At that point plants began to leave the sea in order to colonize the bare earth. It took another 100 million years for the plants to prepare the earth for the introduction of the first animals emigrating from the sea.
Sea sponges have remained in their marine homeland throughout the specie’s entire existence. The question of when did sea sponges first appear on earth is an interesting one for me – they occupy a critically important place in the evolution of animal life.
The Cambrian Explosion
Five hundred and forty-one million years ago an event unlike any other in the history of earth was taking place. Known as the Cambrian explosion, this extraordinary occurrence saw the greatest number and variety of animal life ever introduced on this planet.
To answer the question: when did sea sponges first appear on earth?, one must consider what came before this exceptional period in the history of life on our home planet. Prior to this era life was much simpler; consisting of simple celled organisms that sometimes coalesced into colonies (Wikipedia). This tendency to form interdependent groups of cells shows the direction life was already taking at this point – a higher complexity.
Sea sponges occupy a place somewhere between single celled organisms and animals. They are multi-celled and yet lack any features that are associated with animals, such as a brain and nervous system. Prior to this explosion of animal life, life was relatively simple where no animals existed. Once we entered the Pre-Cambrian period, the first few animals began to appear (PBS).
The first kid on the block
When you see a sea sponge the word animal doesn’t naturally come to mind. They have no symmetrical shape; in fact they come in a vast array of different forms and colors. Sea sponges also lack what we consider to be essential qualities of all animals. Despite this, scientists have determined that these ancient life forms were the first animals to inhabit the earth (Independent).
According to these investigators, sea sponges appeared before the Cambrian explosion. During this time (about 540 million years ago) in earth’s history, life produced its greatest diversity ever. It was during this era when most animals we know today first appeared.
The Proof Is In The Marker
Researchers at the Massachusetts Institute of Technology (MIT) discovered the origins of the sea sponge by analyzing what are known as molecular fossils – trace quantities of molecular materials deposited in rocks millions of years ago that have survived to this day.
One of these molecules were found to be produced specifically by sea sponges and algae. By investigating further scientists found that sea sponges were producing this molecule long before algae (Independent). By analyzing some 600 million year-old rocks containing these molecules, they determined that sea sponges predated the Cambrian explosion.
Great Life-Forms Come In Small Sizes
There are a number of scientific investigators who doubt the reliability of molecular fossils – due to the condition of the molecules after exposure to the elements for such a long time.
A team of researchers claim that a sponge discovered in southern China dates back to a time before the first animals appeared on the planet. They assert that this pea-size sponge inhabited the seas 600 million years ago (Science). This group of scientists are certain this is the world’s earliest known porifera– they point to its three hollow tubes and very porous surface to support the idea that it was indeed a sponge.
This discovery has high implications for the rise of animals; since it highlights the point in earth’s history where sponges and animals branched off a common ancestor. These ancestors of both sponges and animals resembled today’s sponges more than animals – I believe this is one important reason why it is believed sponges are the ancestors to all animals.
When you think about it, it makes sense since sponges are the first multi-celled organism to come into existence. They stand as the bridge between single-celled life and the more complex animals.
All Signs Point to a Sponge
To this day several breakthrough discoveries are giving us solid clues that point to the sponge as being the ancestors to all animals that have ever lived. The Cambrian Explosion saw the greatest proliferation of animal diversity of any period in the history of our planet. The overwhelming majority of the fauna you see around today originated during this time.
Scientists have been able to trace the sea sponge back 600 million years – well before animals began to appear on earth. They did so by identifying a molecule found in rocks that were formed at this time. This type of molecule could have only been produced by sea sponges.
A sponge found in south China also dates back to Precambrian times. Note that this is an entire sea sponge specimen – which is more than a single molecule, which can be physically compromised after such a long period. Investigators claim that there’s little doubt that it’s a sponge, since it possesses the defining physical features of many other sponges, such as tubes and pores.
Mounting evidence is shining a light on the origins of animals. When we look at the big picture and put all we know together, it seems obvious that sea sponges should be recognized as been the occupants of this critically important time in earth’s history.
Sea sponges are unlike any other creature – including us. Yet, they are responsible for giving rise to all other animals. In order to attempt to understand this one must take a deeper view of life. Which functions at such a level of time and magnitude as to go unnoticed by our senses.
What do you think about the connectedness between us and sea sponge? How does it affect your view of life?
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