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This salamander arived in South America before the Panama Isthmus formed, if current opinions are right. Photo: STRI Archives |
The thing about science is that it tends to converge on a single answer, no matter what the starting point. Religions, on the other hand, rarely, if ever converge. If anything, they tend to diverge and splinter into different, mutually hostile factions, each clinging to its 'answer', each unable to muster up arguments why their answer is the right one while all the others have it wrong and each never being able to find that definitive, clinching piece of evidence that would make their arguments indisputable and win over the dissenters.
The reason for this is very simple, and is the reason there isn't only one religion: science is evidence-based and able to change its collective mind when the evidence changes, while religion has no such evidence by which to decide matters of opinion, and can't change its mind because the conclusion is a sacred dogma, central to the religion itself.
An illustration of how science converges can be seen in the paper published a couple of days ago in PNAS. Based on the work of a couple of groups, it has been assumed that the Isthmus of Panama emerged about 3 million years ago and much of our understanding of changes in Earth's climate is based on this assumption.
Closing the connection between the Pacific and Atlantic oceans had profound effects on ocean currents. For example, the Gulf Stream which flows northeast up the east coast of North America then across to Western Europe so keeping much of Northwest Europe several degrees warmer in winter than would otherwise be expected at that latitude. A cold counter-current flows back in the opposite direction. This dynamic is partly responsible for the Atlantic weather systems and has a major effect on marine ecology as well as being hugely influential in the development of the European biota, including Human history.
Prior to the emergence of the Panamanian Isthmus this current would have flowed into the Pacific, so Western Europe would have been much colder and global weather patterns would have been very different to those we see today, so understanding exactly when this change occurred is important for understanding how climate changed over much of the world. Warming up Western Europe might also have increased sea levels as glacial ice melted.
However, this assumption of a 3 million year age for Panama is controversial, with other groups reporting evidence of a much earlier emergence.
There are also some inconsistencies in the biological evidence. The emergence of Panama created a land bridge by which South American species, which had been evolving in isolation since the break-up of Gondwanaland were able to move up into North America and the North American species were able to move south in what is termed, 'the Great American Biotic Interchange'. Obviously, if this biotic interchange started earlier than 3 million years ago this would be fairly strong evidence that the land bridge was there much earlier than is generally assumed.
This is exactly what this PNAS paper presents evidence for:
Significance
The formation of the Isthmus of Panama, which linked North and South America, is key to understanding the biodiversity, oceanography, atmosphere, and climate in the region. Despite its importance across multiple disciplines, the timing of formation and emergence of the Isthmus and the biological patterns it created have been controversial. Here, we analyze molecular and fossil data, including terrestrial and marine organisms, to show that biotic migrations across the Isthmus of Panama began several million years earlier than commonly assumed. An earlier evolution of the Isthmus has broad implications for the mechanisms driving global climate (e.g., Pleistocene glaciations, thermohaline circulation) as well as the rich biodiversity of the Americas.
Abstract
The linking of North and South America by the Isthmus of Panama had major impacts on global climate, oceanic and atmospheric currents, and biodiversity, yet the timing of this critical event remains contentious. The Isthmus is traditionally understood to have fully closed by ca. 3.5 million years ago (Ma), and this date has been used as a benchmark for oceanographic, climatic, and evolutionary research, but recent evidence suggests a more complex geological formation. Here, we analyze both molecular and fossil data to evaluate the tempo of biotic exchange across the Americas in light of geological evidence. We demonstrate significant waves of dispersal of terrestrial organisms at approximately ca. 20 and 6 Ma and corresponding events separating marine organisms in the Atlantic and Pacific oceans at ca. 23 and 7 Ma. The direction of dispersal and their rates were symmetrical until the last ca. 6 Ma, when northern migration of South American lineages increased significantly. Variability among taxa in their timing of dispersal or vicariance across the Isthmus is not explained by the ecological factors tested in these analyses, including biome type, dispersal ability, and elevation preference. Migration was therefore not generally regulated by intrinsic traits but more likely reflects the presence of emergent terrain several millions of years earlier than commonly assumed. These results indicate that the dramatic biotic turnover associated with the Great American Biotic Interchange was a long and complex process that began as early as the Oligocene–Miocene transition.
So here we have a case of different strands of science, geology and biology, converging onto a single solution, just as we would expect, since both are based on observation and measurement of real evidence and clearly animals can't migrate across non-existent land bridges. Moreover, we have a process which actively reassesses our assumptions and looks for ways to resolve them to arrive at a new understanding, even if it means a profound reassessment of even more assumptions, because the ultimate goal is truth, not conformity and compliance.
Meanwhile we see religions still, after many centuries, being unable to decide basic questions like which 'prophets' were true and which were false, which is the correct date to celebrate the death of one of them, and whether this or that senior cleric is infallible or not and killing and persecuting people to decide issues and enforce compliance. Meanwhile the elephant in the room - the complete lack of any definitive evidence for any gods in the first place - is ignored and followers are required to subscribe to dogma on pain of excommunication or even death because they have no definitive evidence by which to prove their competing and contradictory claims.
This latter process is considered by theists to be the vastly superior way to determine truth and to understand the Universe - or so those who benefit most from ignorance and superstition would have us believe.
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