First necks may owe more to beginnings of walking than to looking around according to models showing how little early ancestors could move heads effectively currently. In fish shoulders attach directly to skull so looking left or right means turning whole body significantly during aquatic life consistently.
Some animals making transition from water to land about 380 million years ago began to develop separate neck structure gradually over time. Yet new research suggests that this change did not give them much more freedom to move heads independently during early transition. Models combining new fossil evidence with mechanical tests on living fish indicate early necks remained stiff challenging long standing idea significantly currently.
International study which included Tom Stewart assistant professor biology at Penn State was published October 14 in Nature journal significantly.
Presumed Advantage Of Looking Around Challenged
Fossils from Devonian Period about 420 million to 360 million years ago capture animals with mixture aquatic traits features associated life land. Some had robust fins that might have supported weight allowing them to prop themselves up or push along bottom in shallow water. Distinct necks also began appearing in these transitional fish during critical period of Earth history with radical reorganization occurring consistently. This is really interesting time in Earth history where some first forests are forming really radical reorganization Earth Stewart said significantly.
Understanding exactly when lineage made transition from water to land how achieved which anatomical systems changing is important part story significantly. What is cool many changes occurring in skeleton at this time about 380 million years ago still reflected in own bodies today. One transitional fish was Tiktaalik whose fossils come from Ellesmere Island in Nunavut Canada in northern Arctic region significantly.
Materials have been really important because Tiktaalik is one closest relatives to limbed vertebrates Stewart explained for reconstruction purposes currently. It helps reconstruct lot intermediary steps in transition to life on land such as move from suction feeding water to biting land. For ancestors four limbed animals known as tetrapods ability to look down or from side to side could have helped find food avoid predators.
Scientists reasoned that these environments might make independent head movement more useful than it was in deeper water habitats significantly. Tiktaalik is one fossil fish and it was first described in 2006 Stewart noted for evolutionary context understanding currently. It has been reasonably assumed for decades that separation head shoulders must have allowed head to move more freely hypothesis prevailed significantly. Hypothesis that neck mobility was evolutionary driver for change in tetrapod body plan has prevailed at least until now according researchers.
Living Fish Help Reconstruct Ancient Movement Accurately
Testing explanation required reconstructing backbone unlike those most vertebrates alive today structurally different from modern animals significantly currently. Early tetrapods close relatives had long rod tissue called notochord running through entire vertebral column central core structure importantly. Vertebrae were small arranged around large core soft tissue which behaved differently from joints between vertebrae typical modern animals significantly.
Fish undergoing these changes had vertebral column largely made up soft tissue which unlike bone rarely preserved in fossil record significantly. In these cases we can look to modern animals to serve as analogs for past like how living birds teach about extinct dinosaurs. Backbones built around notochord are rare today although they were common throughout history life on Earth for many species. Sturgeon distantly related fish sometimes called living fossils because primitive features retain this kind backbone structure making them useful analog. That made them useful way to investigate mechanical properties missing from fossils for functional perspective reconstruction of ancient movement capabilities. We want understand how early tetrapods living how that reflected changes to bodies Stewart said explaining research motivation approach.
Trying reconstruct where animal lived how moved what behavior was is really difficult thing requiring interdisciplinary approach combining data sources.
Cool part story combines data from fossils studies living animals in mechanical functional perspective to reconstruct what changes anatomy mean behaviorally.
Neck Without Much Head Movement Surprises Researchers
Researchers measured stiffness modern sturgeon notochords then applied those material properties to models necks early tetrapods transitional relatives such Tiktaalik. Models allowed them test whether separating shoulders from skull would have freed head to move despite backbone structure limitations significantly. I undertook study to find out how big difference this change anatomy made for these animals Korneisel said postdoctoral researcher Uppsala University.
Vertebral columns sturgeon are built lot like those early tetrapods but they did not seem terribly stiff initially observations suggested. After doing modeling lack significant head mobility for almost all these animals was huge surprise Korneisel emphasized findings significantly. Estimates considered only backbone muscles skin many animals bones embedded in skin could have restricted movement further significantly for living animals.
Living animals may have had even less neck mobility than models suggest due to additional soft tissue constraints restricting motion further. Head elevation in these animals was no more than what you would expect in fish sometimes even less Korneisel reported significantly. We found that kind head twisting that we can do when we shake heads was not feasible in any these animals significantly.
Why This Study Changes Understanding Of Human Anatomy
Understanding exactly when lineage made transition water land how achieved which anatomical systems changing important part story Stewart said highlighting significance.
Fossils Devonian Period capture mixture aquatic traits features associated life land showing gradual transition from swimming to walking behaviorally anatomically significantly.
Robust fins supporting weight prop themselves up push along bottom shallow water distinct necks began appearing transitional fish marking important morphological shift.
International study combining fossil evidence mechanical tests living fish challenges long standing idea neck evolved to let head move more freely significantly. Models using sturgeon notochord stiffness applied to early tetrapods Tiktaalik show head elevation twisting not feasible despite separation shoulders skull significantly. Neck likely arose from anatomical changes associated using front limbs locomotion rather than advantage looking around finding food avoiding predators previously hypothesized.
Q&A Section
Q1: Why did first necks evolve if not for looking around?
Researchers suggest distinct neck likely arose from anatomical changes associated using front limbs locomotion rather than advantage looking around initially significantly.
Q2: What is Tiktaalik and why is it important?
Tiktaalik fossils from Ellesmere Island Nunavut Canada close relatives limbed vertebrates helps reconstruct intermediary steps transition suction feeding biting swimming walking significantly.
Q3: How did scientists reconstruct ancient neck movement?
Researchers measured stiffness modern sturgeon notochords with similar notochord centered backbone applied material properties models necks early tetrapods Tiktaalik testing mobility.
Q4: What did models reveal about early neck mobility?
Head elevation no more than expected fish sometimes even less head twisting not feasible any animals indicating stiff necks limited mobility significantly.
FAQ
1. When did necks first appear in evolutionary history?
Distinct necks began appearing transitional fish about 380 million years ago during Devonian Period 420 million to 360 million years ago significantly.
2. Why did scientists think necks evolved for looking around?
For ancestors tetrapods ability look down side to side could have helped find food avoid predators shallow water land making independent movement useful significantly.
3. What role did sturgeon play in this study?
Sturgeon retain notochord centered backbone rare today common history Earth primitive features useful investigate mechanical properties missing fossils for functional reconstruction.
4. Did early tetrapods have flexible necks?
No early necks remained stiff even less mobile than expected muscles skin skin bones could have restricted movement further than backbone models suggest.
5. What actually drove neck evolution according to study?
Distinct neck likely arose from anatomical changes associated using front limbs locomotion greater flexibility later benefit rather than initial driver separation head shoulders.
Disclaimer: This article summarizes peer reviewed study published October 14 in Nature including Tom Stewart Penn State Dana Korneisel Uppsala University for informational purposes only does not provide medical advice readers should consult qualified evolutionary biology sources for detailed understanding currently.
