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Penyebab Kepunahan Kera Raksasa Akhirnya Terjawab

Penelitian baru menunjukkan bahwa kera terbesar yang pernah menghuni Bumi, Gigantopithecus blacki, punah ketika rekan-rekannya yang lebih kecil bisa beradaptasi dengan perubahan lingkungan. 

Kera ini, seberat 300 kilogram dan tinggi sekitar tiga meter, tidak bisa bersaing dengan kera lain yang lebih lincah seperti orangutan dalam menghadapi kondisi yang semakin beragam.

Meskipun penelitian ini mengungkap waktu dan penyebab kepunahan G. blacki, kisahnya tetap menjadi “misteri” paleontologi. Perubahan iklim,  yang mengubah ekosistem hutan dan kelangkaan makanan, dianggap sebagai faktor utama kepunahan tersebut.

Penelitian, yang dipimpin oleh paleontolog Yingqi Zhang dari Chinese Academy of Sciences, merekonstruksi lingkungan tempat G. blacki hidup sekitar 2 juta tahun yang lalu. Era ketika primata ini pertama kali muncul dalam catatan fosil, dan pada masa Pleistosen, era ketika punah. Mereka menganalisis fosil dan sampel sediment dari 22 gua di selatan China, yang terdapat fosil G. blacki.

Catatan fosil memang tidak dapat dengan pasti memberi info mengapa suatu spesies punah. Namun menentukan kapan suatu spesies menghilang dapat membantu peneliti mengidentifikasi  periode perubahan lingkungan dan perilaku yang terkait dengan kepunahan itu.

Berdasarkan penanggalan radiometrik 157,  menggunakan enam teknik yang berbeda, para peneliti memperkirakan bahwa G. blacki punah sekitar 295.000 hingga 215.000 tahun yang lalu.

Analisis serbuk sari mengungkapkan bahwa menjelang dan pada saat kepunahan G. blacki, hutan di selatan China berubah, dan ekosistemnya tidak lagi sesuai dengan habitat G. blacki. Hutan yang semula lebat dengan kanopi tebal, air yang cukup, dan buah-buahan melimpah, menjadi agak kering dengan hutan yang terbuka, padang rumput yang rentan terbakar, serta iklim yang berubah-ubah.

Perubahan iklim inilah yang menjadi bencana bagi G. blacki, termasuk kerabat primata terdekatnya yang juga punah, orangutan Cina (Pongo weidenreichi). G. blacki tidak mampu beradaptasi dengan perubahan lingkungan, bisa dilihat dari analisis perubahan gigi.

Gigi G. blacki menunjukkan tanda-tanda stres kronis menjelang kepunahannya. Pola makannya juga menjadi kurang bervariasi, seiring dengan berkurangnya habitat hutan. Jumlah populasi berkurang, dan jangkauan geografis G. blacki menyusut.

“Itu petunjuk pertama tentang perilaku G. blacki sebagai spesies yang hampir punah. Kontras dengan P. weidenreichi, yang oleh dulu punah,” dipaparkan peneliti dalam makalah mereka.

Meskipun G. blacki tidak terpapar atau terancam di hutan terbuka, catatan peneliti, kera ini bergantung pada buah-buahan  yang menjadi langka seiring dengan perubahan hutan.

“G. blacki gagal beradaptasi, berbeda dengan orangutan atau kera lain yang mampu sintas beradaptasi, dan ini yang menyebabkan kepunahannya,” kata Zhang.

Meskipun perubahan lingkungan menjadi penyebab fatal bagi G. blacki, peneliti menganggap, masih banyak yang bisa dipelajari dari kisah kepunahannya. Untuk dipelajari bagaimana ketahanan primata terhadap perubahan iklim, baik di masa lalu maupun masa depan.

“Adanya ancaman kepunahan massal keenam yang mengintai kita, membuat kita perlu memahami mengapa spesies punah,” demikian kesimpulan studi ini, yang telah dipublikasikan di Nature.

Sumber: https://www.sciencealert.com/what-wiped-out-the-largest-ape-ever-to-roam-earth-we-may-finally-have-an-answer?

 

Lukas Luwarso

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