After Humans

Our sun ignited about 5 billion years ago (8.7 billion years after the Big Bang) and our home planet had formed by 4.6 billion years ago.  Life first evolved in the primordial seas of Earth about 3.6 billion years ago and, through the process of natural selection, has since diversified into the millions of plant and animal species that we find today; we humans did not appear until 150,000 year ago, at the earliest.

Since life appeared and began to diversify, the great majority of species have become extinct, some as "failed" dead-end species while others morphed into more viable species before they died out; the volcanic and sedimentary rocks of our planet are replete with fossils and preserved impressions of extinct species, most of which we have yet to discover.  We humans, endowed with a large brain, imagine that we are a chosen species, the endpoint of evolution on Earth, destined to rule the planet until our God comes to whisk us from our animal life.  Unfortunately, this widespread belief distracts us from the importance of protecting our planet and leads many to deny our dependence on its complex ecosystems.

Of course, we also tend to reject the fact that humans are just another species of Planet Earth, subject to extinction like all other forms of life; from a scientific point of view, the only questions are how that extinction will occur and whether we will evolve into another species beforehand.  Unless we begin to address our overpopulation and reign in our impact on natural ecosystems, we will likely succumb to environmental pollution and other man-induced problems; perhaps a massive asteroid strike, nuclear war or super-volcanic explosion will hasten our demise.  It is conceivable that some humans may escape to another planet or solar system before our species dies out or that the evolutionary offspring of mankind will take that journey before our dying sun destroys the Earth; if neither scenario unfolds, we will die with our planet.

The Nature of Invertebrates

Defined as multicellular animals that do not possess a vertebral column, an internal skeleton or a cranium, invertebrates represent 95% of all multicellular animal species on Earth; though unicellular life first evolved in primordial seas about 3.6 billion years ago, marine invertebrates did not appear until 800 million years ago (near the end of the Precambrian Era).  Vertebrates are grouped within one phyla (Chordata) and are represented by about 66,000 species; by contrast, invertebrates are classified within 33 phyla and are represented by more than 1.3 million species.

The largest invertebrate phylum is Arthropoda, which includes more than 1.1 million species of insects, spiders and crustaceans.  However, 14 invertebrate phyla are represented by various types of worms; the largest of these is Nematoda, which includes more than 25,000 species of roundworms.  Among the other invertebrate phyla are Porifera (sponges), Cnidaria (anemones, jellyfish, corals), Mollusca (slugs, snails, squid, clams, octopus ) and Echinodermata (starfish, sand dollars, sea urchins).

The study of invertebrates certainly makes one appreciate the magnificent diversity of life on Earth.  Once we become familiar with all of the invertebrate species, we can move on to unicellular organisms, fungi, plants and vertebrates (of which we are a member species).  In total, we know of more than 1.7 million species of life on our planet (at least 3/4 of which are invertebrates).

Correction:  In the initial post, crustaceans were incorrectly listed with Mollusca; in fact, they are Arthropods. 

Curiosity, Truth and Human Evolution

We humans are curious creatures.  Indeed, if we were not, our species might have become extinct long ago.

It was curiosity that drew early humans out of Africa, enticing them north through the Sahara Desert and eastward along (and possibly across) the Red Sea.  Curiosity about the plants and animals in their environment eventually led to cultivation and domestication, a development that fostered permanent settlements, linked by trade routes.

Over time, we learned to utilize metals, design machines, explore the seas and study the night sky.  Curious about the structure and function of living organisms, we discovered the nature of life itself, setting us on a course toward modern medicine and biotechnology.  Of course, each step in our enlightenment challenged ingrained beliefs and assumptions, a tension that persists today.  In the end, our curiosity about the Universe will prevail, mysticism will fade and our search for truth will guide the future evolution of our species.