A main factor that inhibits an accurate geological record is water. Water destroys or builds, and thus edits the records. It washes away fossils and sediments, erodes the land, making the rivers like a soup of slit and bones. It makes any single place retain mere fragments of the past. Either large parts of a small timeline or a glimpse of a longer period, which in turn our own museums lack degradation; for the number of incalculable generations that have failed to resist decay.
Secondly, the sudden appearance of a group of species would seem to be a fatal contradiction to the transmutation of species, but has been proven wrong by finding forms that are much older than those thought to be pioneer forms. Even genes can fill the gap where fossils haven’t been able to. Further criticism of natural selection is the notion that life started in the Cambrian stage; an explosion of life where most of the division of the animal kingdom started here. This so called explosion has been a failure to geology and not to Darwin’s machine. The Cambrian period is not the start of life, but a time where more life forms could be preserved. Take for example: Trilobites, the first to claim jointed limbs. During the Cambrian period there were several distinct types of Trilobites. Showing that they were in the middle stage of evolution and that their existence can be found in a older stage. The Geological record is a history of imperfect records that are written in changing dialect. Having the last volume, we only have a few short chapters, and for those chapters few pages, have few lines still exist.
Chapter ten focuses more on the power of gradual and sudden change within the fossil record. The theory of descent with modification through natural selection explains how new species gradually come in to existence slowly and successfully. It will also explain that species of different classes don’t change together or even at the same rate, but all species in time will modify to some degree. Thus, the dominant life forms of that species will continue to produce and the inferior species will become extinct. The dominant forms will reproduce new sub-groups and groups. This is an ongoing process where the next modified dominant life forms generally overtake the inferior species, for every life form faces extinction and can not be produced again in later generations. Hence, after long intervals of time, the world will have appeared to change simultaneously. Finally, the laws of variation are in motion around us, and are kept in check by natural selection.
- What other markers can be used to explain or support the age of the earth, and how would you properly construct a flawless agreement when debating with a creationist?
- Where have genes filled the gap created when fossils provided insufficient information about the past?
- Mass extinctions are inevitable and are seen throughout the geological history, and natural selection is seen as a gradual process. How is this still possible, and can you think of any examples?
Tyler's discussion of chapter 9 seems to rehash the 19th century suggestion by Darwin and others that the geological record was very imperfect, and that this incompleteness explains the presence of many "gaps" in the fossil record. But certainly in 2009, this excuse is not nearly as valid as it was in 1859. Let's probe a bit deeper into the supposed absence of intermediate forms in the fossil record. For example, what about human evolution? Are we hampered in our understanding of human evolution by major imperfections or gaps in the human fossil record?
ReplyDeleteI'd like to see some other posts reflecting on these topics, and other ones raised by Tyler's post.
The geological record is “imperfect” and what researchers have collected in the way of evidence is miniscule to how many formulations actually took place over time. This is due to huge lapses in time allowing for the degradation of the fossil record, mass extinction, migration patterns, shifting landforms especially because of water, and the fact that only certain species leave a trace in the ground to be found. The continents as we know them today were vastly altered fifteen million years ago. Jones example of the absence of the passenger pigeon in the record, though known to be in huge numbers in the 19th century, explains why transitional traits are difficult to come by and how what fossils are found “do not reflect reality.” It is important, also, to know that “extinct forms are seldom directly intermediate between existing forms (234)” and what has become extinct cannot evolve again in the same way. But shouldn’t it be noted that all the fossils that are located are direct evidence of transition, that we are continuously in a state of change? And intermediates have been traced (eg. the “half-bird” of Patagonia), but with most of the earth unexplored as yet these gaps will remain for some time.
ReplyDeleteIn response to Dr. Anomone, I would say these gaps in no way hampers the theory of evolution. Just observing what has been found thus far leaves no doubt that early humans appeared and behaved differently then we do today, and the fact that they no longer walk the earth is testament to some form of shift or extinction. What is in doubt relates only to how the tree of human evolution branched out and at what times, not to the theory itself.
Radiometric dating appears to be the main approach to determining the age of the earth (until two-hundred years from now when we find that we were wrong). In addition, meteorites have also been used to determine ages of the earth through rafiometric dating. The doppler effect (red shift)is utilized to measure and monitor the movement of celestial bodies in our known universe.
ReplyDeleteI personally think a flawless argument is impossible for two reasons: Evolution is still a theory that has many unanswered questions and is succeptible to critical reasoning, and arguing faith usually ends up with both parties walking away feeling reinforced in their beliefs. Arguing intangibles from both sides ends in a stalemate.
Mass extictions are often attributed to random fast-acting disasters; these are unknown variables to the laws of natural selection. It seems to me that there is your perpetual, gradual change that is punctuated by a causal force such as a natuaral disaster.
When taken into account how the earth's formation churns and tumble upon itself, it is amazing that the human race has been able to reconstruct a timeline with as many specimens of the path of evoulution on earth. The lack of intermediate forms still intrigues me, but like Bob has explained, it is not as much as a problem as it was to Darwin. Given the minute sample of fossil evidence that we do have, it only makes me wonder how many "dead ends" did the Homo genus go through that we may never find? Given the geologic time frame that Homo sapiens have existed in, are we not just an intermediate garadually transorming into the next practical and effective life-form?
It seems to me that the fact that we do have 'intermediate' forms found within the fossil record proves de facto that evolution through descent with modification exists. The question rests on the fossils that have been found and what their own evolutionary and ecological niches in fact were within the evolutionary timetable. Because we exist, we are an intermediate form in evolution through descent with modification as Zach's question implies. By looking at our very own evolutionary and ecological attributes (bipedal, large brain, vocal chords, etc) we can learn what our evolutionary ancestors must have developed through their own variation even if it is not available in the fossil record. What we do have in the fossil record, though, gives proof to certain attributes of our evolutionary adaptation, but where gaps exist the answer may be buried in still undiscovered strata - but we can see their attributes in our very own biology. Plus, wouldn't the answers still buried within our DNA?
ReplyDeleteOn the issues that arise pertaining to the imperfection of the geological record, I think that it is less of a problem today than it was in the mid-nineteenth cenutry. As Jones discusses we have a better understanding of the forces of nature that edit the fossil record, such as water, ice, plate tectonics, etc. For example what we now know about the mid-atlantic ridge and its patterns of producing new crust and destroying the old means that fossils contianed within these given sections of the sea floor will be lost forever once they are destroyed. However, I do think that these issues will continue to be the bases for many arguments attempting to discredit the theory of descent with modification. While in the past the imperfections in the fossil record may have presented more of a problem, what we know today gives us the capability to better explain the forces of nature that "edit" the fossil record.
ReplyDeleteRegarding how this affects the absence of intermediates, I think that preferencial preservation, or acts of nature which destory the fossil record do impact this greatly. However, there are known intermediates, such as Archaeopterx, so this suggests that evolution does occur. In regards to Humans the same forces of nature that impact other living species must impact Humans. We do have fossil evidence that there were ancient hominids, even if they might not be a direct ancestor it still suggests that hominids were also impacted the forces of evolution, and that these homonids may infact represent intermediate forms in some way, such as increaing brain mass. However, I do also think that DNA and genetics may be the way to answer the questions regarding human evolution.