Losing LUCA

Origin-of-Life Science Pushes Cellular Complexity Back to the Beginning of Life

In the last few years, evolutionary biologists have had to contend with a barrage of new scientific research that calls into question many of the core beliefs holding their theories together. In a previous Salvo blog, we took a look at the work of Dr. James Tour, who single-handedly exposed the many ways origin-of-life researchers resort to human intervention to create even the simplest of life’s molecules whilst also pointing out that science is nowhere near showing how something as complex as a single cell could come into existence entirely by natural means. Other Salvo articles have chronicled the debunking of core tenets of the evolutionary paradigm, including so-called junk DNA and the waiting-time problem for the emergence of new biological traits, amongst many others. Now, one of the most fundamental concepts in evolutionary biology is coming under similar scrutiny: the origin and nature of the Last Universal Common Ancestor (LUCA).

The Characteristics of LUCA

If the evolutionary paradigm is to hold any water, there must have been a cell – a cellular LUCA - that possessed the information needed to produce the basic features of all extant microbes and that subsequently evolved into the myriad fungi, plants, and animals that exist today. Such an organism, they surmise, would not have been the first lifeform but would have arisen from previously existing primitive cells – so called progenotes – that gave rise to this LUCA via acquisition of pre-existing genes from several other more primitive, pre-existing progenotes.

One approach adopted by researchers in their attempts to more fully understand the characteristics of LUCA is to identify all the genes held in common by bacterial and archaeal species. If LUCA gave rise to the evolutionary lineages that produced bacteria and archaea, they reason, then the sets of genes they share must have contributed to LUCA’s genome. Such studies have identified anywhere from 350 to 1000 genes, depending on the study design.

Others have approached characterizing LUCA by studying the physiology of archaea and bacteria. These studies have identified several traits LUCA would have needed in order to have been the ancestor of future lifeforms. These might include such traits as the ability to move, the presence of a single cell membrane consisting of lipids, tolerance to salt water and higher temperatures, and the ability to thrive in an atmosphere devoid of oxygen.

How evolutionary biologists envision the origin of LUCA. Image credit Wiki Commons.

The Dating of LUCA

What is more mysterious is the time period during which LUCA emerged. Some researchers estimate that it must have existed at least 3.8 billion years ago, while others insist it must have been considerably earlier – anywhere from 4.2 to 4.4 billion years ago. To pin down these dates, a team of scientists from the UK used molecular clocks to suggest that LUCA emerged about 3.9 billion years ago. The trouble with this date is that it also coincides with the period when the inner solar system was pummelled by myriad asteroids and comets in an event known as the Late Heavy Bombardment. If LUCA emerged during this period, it must have endured hellish conditions where large parts of the Earth’s surface were cauterized and when most of the surface water ended up in the atmosphere as steam. This pushes the origin of progenotes back even further in time to when the surface of the planet was molten.

Now yet another study conducted by a team of scientists from the UK and the United States, has waded into the nature of LUCA by trying to reconstruct its likely physiology. Their conclusions are eye opening to say the least:

Our results have the potential to push cellular complexity back to the very beginning of life. Barring the unlikelihood of panspermia, these results imply that complex phenotypic traits arose far earlier in the history of life than previously thought. . . . early life may have very quickly evolved considerable cellular complexity. We thus reveal LUCA as a potentially complex cell possessing a genetic code perhaps more intricate than many modern bacteria and archaea.

But these revelations raise more questions than they answer. Dr. Fazale Rana, biochemist and president of the science-faith organization Reasons to Believe (RTB), points out the problem when he asks, how could such astonishing cellular complexity occur right at the beginning of our planet’s history, when the evolutionary narrative insists that microbial life acquired more complexity over time?

Informed from the Start

But cellular complexity near the beginning of Earth’s history readily fits RTB’s old earth creation model, in which God introduced fully complex life at the point in time that our planet could support it.

The suggestion that earth’s earliest lifeforms needed to have hundreds or thousands of genes raises legitimate questions as to where this genetic information came from. Furthermore, other studies have shown that to maintain viability, cells must contain a minimum of about  800 genes and several dozen regulatory sequences just to stay alive. The standard evolutionary answer is that LUCA acquired these genes from less sophisticated, coexisting progenotes. But what is the source of that genetic information, and how could it have formed without any guiding intelligence in such a harsh environment? At some point, it stretches credulity to suggest that any of this occurred by accident, or indeed, even gradually.

The prophet Isaiah, however, provides an intriguing answer:

We live in very exciting times. More than at any time in the past, origin-of-life science points to a Creator very much like the God of the Bible.